nebraska: Add Nebraska class

This allows us to easily use nebraska as a library instead of an
HttpServer. Now the NebraskaServer wraps around Nebraska to post/receive
request/response instead of itself creating them.

This also makes it easier to later write tests/unittests for it.

Also cleaned up some code in unittest_common.

BUG=chromium:920404
TEST=unittest
TEST=nebraska.py --port=1000 and sent some requests to it.

Change-Id: I8f7862055219dbd6b470b85fa5c34d9f9cb57b2b
Reviewed-on: https://chromium-review.googlesource.com/1518804
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Nicolas Norvez <norvez@chromium.org>
3 files changed