`Network` constructor and `def show` have contradictory default values for the `notebook` arg.

[colllin]

The Network constructor (def __init__) has default kwarg notebook=False. The def show method has default kwarg notebook=True.

It seems like this is causing confusion for some people. It would make sense to me that the .show() method by default uses the same notebook setting that was passed as a kwarg to the notebook.