Correct instructions for generating docs.
Undo my hack to work around https://github.com/nose-devs/nose/issues/556.
Fix some path issues with “python3 setup.py test”.
Delete check_required_callback test helper.
Note no GridFS.put() with w=0 in Motor.
Obsolete TODO.
Update PyPy info.
Remove callback_from_future.
Missing call to super().__init__