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 don't like 'assumes' here - it's not technically an assumption of the model. Also, I don't think that it's accurate to say that no one uses the word 'posits': https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=%22the%20model%20posits%22