Restore testing matrix. Add PyPy3.
Restore testing matrix. Add PyPy3.

lewiscollard/cms,jamesfoley/cms,jamesfoley/cms,dan-gamble/cms,dan-gamble/cms,jamesfoley/cms,lewiscollard/cms,danielsamuels/cms,danielsamuels/cms,danielsamuels/cms,dan-gamble/cms,jamesfoley/cms,lewiscollard/cms