Tox environnement to run python based tests

Adds a tox environement much like we already did for
analytics/wikimetrics and mediawiki/tools/scap repositories.  That is
simply running the make-release tests for now.

Whenever this change land in, we can add the python testing jobs for
the py27 and flake8 tox envs.

Change-Id: I17401186a11f0ad632348b2d5a7874fd1cbe4ad3