Shapley

Closes #57 (closed)

Introducing SHAPley framework to understand importance of features to the model ouput.

You just need to add a --shapley flag to evaluate_model.py --dl1 and it will output two plots into modelname/plots/. In principle it should also be compatible with dips, if it uses the same datatypes and structures for model and X_test. I will refer you from now on to the docs.