LiFE

This is just to let you know that I am working on an implementation of the Linear Fascicle Evaluation algorithm, described in our recent paper: http://www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth.3098.html

There might be an opportunity to speed things up, using cython. In particular, I am thinking about ways to speed up both sl_signal and voxel2fiber, and any suggestions on that are most welcome. 

I find the parameter n_points misleading. Is the number of sphere points that crucial? Can you not just have a parameter called sphere and if None just use the 724 sphere?