Add some more sklearn API to the CNN model?

[arokem]

We can't currently use cross_val_score because:

TypeError: Cannot clone object '<afqinsight.cnn.CNN object at 0x7fca351d1be0>' (type <class 'afqinsight.cnn.CNN'>): it does not seem to be a scikit-learn estimator as it does not implement a 'get_params' method.

I wonder how many more methods we'd need to implement for this (and other things? For example sklearn pipelines?) to work.