Simple ML exercises
Following this video series https://www.youtube.com/watch?v=cKxRvEZd3Mw&list=PL8nXlbcZDCrzIqQJUs7tWsaueVhUAPKvB&index=1 Adapting example from http://chrisstrelioff.ws/sandbox/2015/06/08/decision_trees_in_python_with_scikit_learn_and_pandas.html