COMPAT/TST Matplotlib 2.0 compatability
- [x] closes #13333
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

Just a WIP for now, I want to cleanup how I handle the errorbar changes.

Will wait for a matplotlib RC before changing the Travis matrix I suppose? 
