Tox jobs for mediawiki/tools/release

Bring it python unittests and flake8 \O/

Creates jobs:
    mw-tools-release-tox-flake8
    mw-tools-release-tox-py27

Deletes:
    mw-tools-release-pep8
    mw-tools-release-pyflakes
    mw-tools-release-sphinx-doc

Change-Id: I2d1d43ae608bea16942ee8e1f4c672da2767767c