Setup auto-version increment on release

[fbertsch]

Currently the setup.py version needs to be incremented on release. That's annoying, it would be nice to just release when we'd like - perhaps on creation of a tag.

[jezdez]

I can recommend using setuptools_scm, check out https://github.com/mozilla-services/python-dockerflow or https://github.com/mozilla/jupyter-spark how to use it.