Build protobuf files in as part of tox runs.

Signed-off-by: Dan O'Reilly <oreilldf@gmail.com>

python/tox.ini

@@ -8,6 +8,7 @@ setenv =
     LD_LIBRARY_PATH={toxinidir}/../src/.libs
 commands =
     python setup.py -q --cpp_implementation develop
+    python setup.py build_py
     python setup.py -q test -q
 deps =
     six