Change print statements to logging

[softwaredoug]

There are a lot of helpful print statements throughout the code that we should change to logging. I would prefer using the built-in Python logging libraries to cut down on dependencies, but are open to various options.

It should be possible to switch on/off logging in a notebook to see what's happening. Logging should by default go to the notebook itself (ie std out, like a print statement).

Not too stressed about what the right granularity is right now, if everything was "INFO" or "ERROR" then that'd be awesome. So long as we can get things into logging statements...