Added functions for calculating and displaying squared error as well as its corresponding tests.
Altered log_prop_val to allow model fitting of the SFM's dispersion index
Some functions for creating scatter density plots as well as some various fixes.
Changed separate_bvals and test so it would output the rounded and scaled b values.
Changed class init and response function to take in multiple b values.
Some more additions
Edited functions related to signal functions from base model to fix regressor function.
Edited all the functions in sparse_deconvolution.py.
Changed _flat_signal
Fixed matrix dimensions/arrangements of model_params.
Edited fit and predict functions.
Changed model params and fit so that the outputs are interweaved.
Made the inputs to _calc_rotations more general.
Progress on predict and fit
Model_params and fit work - design matrix now transposed when taking dot product (rot_vecs by vertices).
Tests for multi_bvals through fit
Many changes.  Not so sure
Get arrays instead of lists for internal variables.
Fixed predict
Various fixes