Sparse Fascicle Model

This is a start on an implementation of the model we describe here: 

http://arxiv.org/abs/1411.0721

The main current issue with this is that this will have a local dependency on scikit-learn, because it uses ElasticNet for the fit. How do people feel about that? 
Here you start with your default response which is [0.0015, 0.0005, 0.0005] wouldn't be better and more generic to use the auto_response function to estimate this response rather than having a fixed one? In that way this will work with other data too where the response might be a bit different than [0.0015, 0.0005, 0.0005].