Fix to typo/oversight in python tests, only affecting python 3

In Python 2.6 the positional argument specifiers are apparently required
to be explicitly specified:
http://stackoverflow.com/questions/10054122/valueerror-zero-length-field-name-in-format-python

This includes all internal changes from around May 20 to now.

OS X's version of Python has a slightly different error
message for this error case.

Python 2.x doesn't detect unpaired surrogates so we have to
do that manually.

--allow_oversize_protos=true is passed to bazel build.
When this macro is set, SetTotalBytesLimit is called to remove
the 64MB limit on binary protos when during ParseFromString.

Also delete some unused files.

Change-Id: Ia9e2795b1ff1abb30410ffb3ef96ba6f46dd99d0

Version number for beta languages is updated to v3.0.0-beta-2.
Version number for alpha languages is updated to v3.0.0-alpha-5.

Fixes #1029

Also made the Travis build ensure that no warnings
are present.

These builds were previously spewing many warnings,
which was hiding warnings for important things like
accidentally using C++11-only features.

Change-Id: I56caeee9db48bc78756a3e8d7c14874630627037

1, objcect_pair_hook is not supported in python2.6, so duplicated key check is removed in 2.6
2, total_seconds is not suppoted in python2.6, changed to compute seconds directly