removed unnecessary import; formatting changes; docstring fix
save cairo context fewer times, and use a contextmanager
remove QuantumBitMachine.from_state() class method

especially since it doesn't seem to copy the numpy array it is given
(or verify that it is indeed a numpy array)
removed ipython notebook rendering stuff that uses jsqis.

the pycairo stuff is better, and easier to set up.
added a QuantumBitMachine._clone() method
updated the conventions for performing operations