wrapping CREMA models as PUMPP feature extractors

[tomxi]

This is to facilitate #24, as it uses the CREMA/chord model as a feature extractor.

Suggesting there should be a new module pumpp.py which access the chord model from analyze, and wraps the model in as a pumpp feature extractor. (related: bmcfee/pumpp#110)

There should also be a model getter function to interface with __MODEL__ in analyze, so the feature extractor can have access to the model.

[tomxi]

no need after #24 is closed.