Python 3 compatibility changes

Made a couple changes to allow this to run with Python 3. All tests pass and I was able to run the example notebooks in both Python 3.3 and Python 2.7. However, some changes are required to the moss and pyhusl libraries which I have forked and updated to make the necessary changes to run on Python 3. 

I'm not sure what the best way to deal with other libraries being behind for others trying to install seaborn.