Add version responder

This responder display bot version based on closest git tag, but the version defined in the setup file doesn't match the git tag, perhaps it's possible to use the same system in the setup file ?
I've seen post about fetching current package version on stackoverflow: http://stackoverflow.com/questions/458550/standard-way-to-embed-version-into-python-package
http://stackoverflow.com/questions/2058802/how-can-i-get-the-version-defined-in-setup-py-setuptools-in-my-package
but as the value doesn't match/is lower than the git tag, I fetch it through git.