Bump minimal Python 2.x version to 2.7

This lets me banish a local version of OrderedDict, which has issues submitted
against it (e.g. pull request #53).

Python 2.7 has been out for a while now, it's time to move on. I haven't been
testing pyelftools on 2.6 for some time anyway.
diff --git a/CHANGES b/CHANGES
index 926dbe0..72e030b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,14 @@
 Changelog
 =========
 
++ Version 0.23 (??)
+
+  - Minimal Python 2.x version raised to 2.7
+  - Basic support for MIPS (contributed by Karl Vogel).
+  - Support for PT_NOTE segment parsing (contributed by Alex Deymo).
+  - Support for parsing symbol table in dynamic segment
+    (contributed by Nam T. Nguyen).
+
 + Version 0.22 (30.03.2014)
 
   - pyelftools repository moved to https://github.com/eliben/pyelftools
diff --git a/README.rst b/README.rst
index d668f3b..4ed20a1 100644
--- a/README.rst
+++ b/README.rst
@@ -10,7 +10,7 @@
 --------------
 
 As a user of **pyelftools**, one only needs Python to run. It works with
-Python versions 2.6, 2.7 and 3.x (x >= 2). For hacking on **pyelftools** the
+Python versions 2.7 and 3.x (x >= 2). For hacking on **pyelftools** the
 requirements are a bit more strict, please see the
 `hacking guide <https://github.com/eliben/pyelftools/wiki/Hacking-guide>`_.
 
diff --git a/elftools/common/ordereddict.py b/elftools/common/ordereddict.py
deleted file mode 100644
index 18ee045..0000000
--- a/elftools/common/ordereddict.py
+++ /dev/null
@@ -1,262 +0,0 @@
-#-------------------------------------------------------------------------------
-# elftools: port of OrderedDict to work on Python < 2.7
-#
-# Taken from http://code.activestate.com/recipes/576693/ , revision 9
-# Code by Raymond Hettinger. License: MIT
-#-------------------------------------------------------------------------------
-try:
-    from thread import get_ident as _get_ident
-except ImportError:
-    from dummy_thread import get_ident as _get_ident
-
-try:
-    from _abcoll import KeysView, ValuesView, ItemsView
-except ImportError:
-    pass
-
-
-class OrderedDict(dict):
-    'Dictionary that remembers insertion order'
-    # An inherited dict maps keys to values.
-    # The inherited dict provides __getitem__, __len__, __contains__, and get.
-    # The remaining methods are order-aware.
-    # Big-O running times for all methods are the same as for regular dictionaries.
-
-    # The internal self.__map dictionary maps keys to links in a doubly linked list.
-    # The circular doubly linked list starts and ends with a sentinel element.
-    # The sentinel element never gets deleted (this simplifies the algorithm).
-    # Each link is stored as a list of length three:  [PREV, NEXT, KEY].
-
-    def __init__(self, *args, **kwds):
-        '''Initialize an ordered dictionary.  Signature is the same as for
-        regular dictionaries, but keyword arguments are not recommended
-        because their insertion order is arbitrary.
-
-        '''
-        if len(args) > 1:
-            raise TypeError('expected at most 1 arguments, got %d' % len(args))
-        try:
-            self.__root
-        except AttributeError:
-            self.__root = root = []                     # sentinel node
-            root[:] = [root, root, None]
-            self.__map = {}
-        self.__update(*args, **kwds)
-
-    def __setitem__(self, key, value, dict_setitem=dict.__setitem__):
-        'od.__setitem__(i, y) <==> od[i]=y'
-        # Setting a new item creates a new link which goes at the end of the linked
-        # list, and the inherited dictionary is updated with the new key/value pair.
-        if key not in self:
-            root = self.__root
-            last = root[0]
-            last[1] = root[0] = self.__map[key] = [last, root, key]
-        dict_setitem(self, key, value)
-
-    def __delitem__(self, key, dict_delitem=dict.__delitem__):
-        'od.__delitem__(y) <==> del od[y]'
-        # Deleting an existing item uses self.__map to find the link which is
-        # then removed by updating the links in the predecessor and successor nodes.
-        dict_delitem(self, key)
-        link_prev, link_next, key = self.__map.pop(key)
-        link_prev[1] = link_next
-        link_next[0] = link_prev
-
-    def __iter__(self):
-        'od.__iter__() <==> iter(od)'
-        root = self.__root
-        curr = root[1]
-        while curr is not root:
-            yield curr[2]
-            curr = curr[1]
-
-    def __reversed__(self):
-        'od.__reversed__() <==> reversed(od)'
-        root = self.__root
-        curr = root[0]
-        while curr is not root:
-            yield curr[2]
-            curr = curr[0]
-
-    def clear(self):
-        'od.clear() -> None.  Remove all items from od.'
-        try:
-            for node in self.__map.itervalues():
-                del node[:]
-            root = self.__root
-            root[:] = [root, root, None]
-            self.__map.clear()
-        except AttributeError:
-            pass
-        dict.clear(self)
-
-    def popitem(self, last=True):
-        '''od.popitem() -> (k, v), return and remove a (key, value) pair.
-        Pairs are returned in LIFO order if last is true or FIFO order if false.
-
-        '''
-        if not self:
-            raise KeyError('dictionary is empty')
-        root = self.__root
-        if last:
-            link = root[0]
-            link_prev = link[0]
-            link_prev[1] = root
-            root[0] = link_prev
-        else:
-            link = root[1]
-            link_next = link[1]
-            root[1] = link_next
-            link_next[0] = root
-        key = link[2]
-        del self.__map[key]
-        value = dict.pop(self, key)
-        return key, value
-
-    # -- the following methods do not depend on the internal structure --
-
-    def keys(self):
-        'od.keys() -> list of keys in od'
-        return list(self)
-
-    def values(self):
-        'od.values() -> list of values in od'
-        return [self[key] for key in self]
-
-    def items(self):
-        'od.items() -> list of (key, value) pairs in od'
-        return [(key, self[key]) for key in self]
-
-    def iterkeys(self):
-        'od.iterkeys() -> an iterator over the keys in od'
-        return iter(self)
-
-    def itervalues(self):
-        'od.itervalues -> an iterator over the values in od'
-        for k in self:
-            yield self[k]
-
-    def iteritems(self):
-        'od.iteritems -> an iterator over the (key, value) items in od'
-        for k in self:
-            yield (k, self[k])
-
-    def update(*args, **kwds):
-        '''od.update(E, **F) -> None.  Update od from dict/iterable E and F.
-
-        If E is a dict instance, does:           for k in E: od[k] = E[k]
-        If E has a .keys() method, does:         for k in E.keys(): od[k] = E[k]
-        Or if E is an iterable of items, does:   for k, v in E: od[k] = v
-        In either case, this is followed by:     for k, v in F.items(): od[k] = v
-
-        '''
-        if len(args) > 2:
-            raise TypeError('update() takes at most 2 positional '
-                            'arguments (%d given)' % (len(args),))
-        elif not args:
-            raise TypeError('update() takes at least 1 argument (0 given)')
-        self = args[0]
-        # Make progressively weaker assumptions about "other"
-        other = ()
-        if len(args) == 2:
-            other = args[1]
-        if isinstance(other, dict):
-            for key in other:
-                self[key] = other[key]
-        elif hasattr(other, 'keys'):
-            for key in other.keys():
-                self[key] = other[key]
-        else:
-            for key, value in other:
-                self[key] = value
-        for key, value in kwds.items():
-            self[key] = value
-
-    __update = update  # let subclasses override update without breaking __init__
-
-    __marker = object()
-
-    def pop(self, key, default=__marker):
-        '''od.pop(k[,d]) -> v, remove specified key and return the corresponding value.
-        If key is not found, d is returned if given, otherwise KeyError is raised.
-
-        '''
-        if key in self:
-            result = self[key]
-            del self[key]
-            return result
-        if default is self.__marker:
-            raise KeyError(key)
-        return default
-
-    def setdefault(self, key, default=None):
-        'od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od'
-        if key in self:
-            return self[key]
-        self[key] = default
-        return default
-
-    def __repr__(self, _repr_running={}):
-        'od.__repr__() <==> repr(od)'
-        call_key = id(self), _get_ident()
-        if call_key in _repr_running:
-            return '...'
-        _repr_running[call_key] = 1
-        try:
-            if not self:
-                return '%s()' % (self.__class__.__name__,)
-            return '%s(%r)' % (self.__class__.__name__, self.items())
-        finally:
-            del _repr_running[call_key]
-
-    def __reduce__(self):
-        'Return state information for pickling'
-        items = [[k, self[k]] for k in self]
-        inst_dict = vars(self).copy()
-        for k in vars(OrderedDict()):
-            inst_dict.pop(k, None)
-        if inst_dict:
-            return (self.__class__, (items,), inst_dict)
-        return self.__class__, (items,)
-
-    def copy(self):
-        'od.copy() -> a shallow copy of od'
-        return self.__class__(self)
-
-    @classmethod
-    def fromkeys(cls, iterable, value=None):
-        '''OD.fromkeys(S[, v]) -> New ordered dictionary with keys from S
-        and values equal to v (which defaults to None).
-
-        '''
-        d = cls()
-        for key in iterable:
-            d[key] = value
-        return d
-
-    def __eq__(self, other):
-        '''od.__eq__(y) <==> od==y.  Comparison to another OD is order-sensitive
-        while comparison to a regular mapping is order-insensitive.
-
-        '''
-        if isinstance(other, OrderedDict):
-            return len(self)==len(other) and self.items() == other.items()
-        return dict.__eq__(self, other)
-
-    def __ne__(self, other):
-        return not self == other
-
-    # -- the following methods are only used in Python 2.7 --
-
-    def viewkeys(self):
-        "od.viewkeys() -> a set-like object providing a view on od's keys"
-        return KeysView(self)
-
-    def viewvalues(self):
-        "od.viewvalues() -> an object providing a view on od's values"
-        return ValuesView(self)
-
-    def viewitems(self):
-        "od.viewitems() -> a set-like object providing a view on od's items"
-        return ItemsView(self)
-
diff --git a/elftools/common/py3compat.py b/elftools/common/py3compat.py
index d57567d..4878bf3 100644
--- a/elftools/common/py3compat.py
+++ b/elftools/common/py3compat.py
@@ -15,9 +15,6 @@
     StringIO = io.StringIO
     BytesIO = io.BytesIO
 
-    import collections
-    OrderedDict = collections.OrderedDict
-
     _iterkeys = "keys"
     _iteritems = "items"
     _itervalues = "values"
@@ -34,8 +31,6 @@
     import cStringIO
     StringIO = BytesIO = cStringIO.StringIO
 
-    from .ordereddict import OrderedDict
-
     _iterkeys = "iterkeys"
     _iteritems = "iteritems"
     _itervalues = "itervalues"
diff --git a/elftools/dwarf/die.py b/elftools/dwarf/die.py
index 86830fc..1b42066 100644
--- a/elftools/dwarf/die.py
+++ b/elftools/dwarf/die.py
@@ -6,11 +6,11 @@
 # Eli Bendersky (eliben@gmail.com)
 # This code is in the public domain
 #-------------------------------------------------------------------------------
-from collections import namedtuple
+from collections import namedtuple, OrderedDict
 import os
 
 from ..common.exceptions import DWARFError
-from ..common.py3compat import OrderedDict, bytes2str, iteritems
+from ..common.py3compat import bytes2str, iteritems
 from ..common.utils import struct_parse, preserve_stream_pos
 from .enums import DW_FORM_raw2name
 
diff --git a/tox.ini b/tox.ini
index 600ca1c..d1f85bf 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,7 +6,3 @@
     python test/run_all_unittests.py
     python test/run_examples_test.py
     python test/run_readelf_tests.py
-
-[testenv:py26]
-deps =
-    unittest2