Notable Changes:
  -Convert all str types to byte types at cython layer (ascii encoding)
  -Use six for packages that have different names in Python2/Python3
  -By default, unit tests are compiled/run in Python2.7 and Python3.4
  -Ensure MACOSX_BUILD_TARGET is at least 10.7

Removed constants kPackageName and kServiceName so multiple services
can be defined in one proto.

Used for non-default 1 MB UDP socket buffers.