WIP: Add git versioning
FIX: Seems to be working [ci skip]
FIX: Fix commit number
ENH: Add example
FIX: Fix version
FIX: Fix version (update)
Merge pull request #161 from Eric89GXL/gits

ENH: Add git versioning.  
LGTM.  Don't forget to change the URL in `_git.py` to `LABSN/expyfun.git` and to change the commit number in `test_version`