Merge pull request #3 from rmcgibbo/tutorial2

Fix tutorial for msmbuilder2.8
Merge branch 'master' of github.com:SimTk/msmbuilder
Merge branch 'master' of github.com:SimTk/msmbuilder
python3 fix for Tutorial/PlotDihedrals.py
Merge pull request #394 from rmcgibbo/py3

Py3