Add python implementation of commit message validation.

    validate-commit-msg.py is a python script that can verify commit messages.

    Installation:
    - cd <project dir>
    - cd .git/hooks
    - ln -s ../../app/Resources/validate-commit-msg.py commit-msg

    Source https://gist.github.com/onjin/5442494

    See also https://docs.google.com/document/d/1QrDFcIiPjSLDn3EL15IJygNPiHORgU1_OOAqWjiDU5Y/edit