Change the writeable flag back to its original state when finished.
Test a more flexible approach allowing list of mixed dtypes.
Comparison of three version of functions length and set_number_of_points in Cython.
Make a new benchmarking function to compare Orignal, MrBago and the flexible version of functions length and set_number_of_points in Cython
Update benchmarking function
Improved flexible version
Made test_streamline Python3 compatible
Merge pull request #431 from MarcCote/fix_streamlinespeed

Change the writeable flag back to its original state when finished.
NF: unique rows of an array.
NF: Added a crutch function. This will need to be removed later on.

And replaced with `move_streamlines`, but I am defering that until I get a
sense of what is happening here.
NF: Added a first-pass implementation of LiFE.
RF: Thinking about simplifying this.

Maybe use dipy.sims.voxel directly?
WIP: Completed the mapping function voxel2fiber, inclduing test.
Matrix allocation more-or-less working.
WIP: Still working out how to create this model.
NF: Added Sparse SGD algorithm for solution of the LiFE equations.
TST + BF: Make sure that input to np.gradient is an array.
RF: Move down the fit function.
RF: docs
Might not need to isotropic matrix, if we treat that as a mean.