Less wasted space in test_motor_tail
Test MotorCursor.tail()'s callback checking
Comment improvement in test_motor_tail
Add await_data in test_tail_gen
MotorCursor.tail() should return self, and close() should cease tailing immediately. Also tail() throws err if cursor is started.
Some docstrings for clone and rewind
Remove an unused version of test_each and test MotorCursor's callback-checking more thoroughly
Less wasteful whitespace
Refactor callback-checking in tests