Handle Google PRE_ tests (#80)

Support skipping PRE_ tests used by Chromium
diff --git a/gtest_parallel.py b/gtest_parallel.py
index 25887ea..6e2351f 100755
--- a/gtest_parallel.py
+++ b/gtest_parallel.py
@@ -611,6 +611,10 @@
       if not options.gtest_also_run_disabled_tests and 'DISABLED_' in test_name:
         continue
 
+      # Skip PRE_ tests which are used by Chromium.
+      if '.PRE_' in test_name :
+        continue
+
       last_execution_time = times.get_test_time(test_binary, test_name)
       if options.failed and last_execution_time is not None:
         continue