Update credits to current state of affairs#3900

Merged

JukkaL merged 3 commits intopython:masterfrom gvanrossum:update-credits

Sep 1, 2017

+19-65

Commits on Aug 31, 2017

Update credits to current state of affairs
Guido van Rossum
committed
Add some recent frequent contributors
Guido van Rossum
committed

Commits on Sep 1, 2017

Clean up CREDITS more
Guido van Rossum
committed