fixelcfestats now supports -mask option
Due to popular demand (including my own), fixelcfestats now has a new option -mask. Note that this is a fixel mask, not a 3D voxel mask image.
Additionally, during the process of implementing this, I changed some of the internal fixel stats code such that, for my own test case, I experienced a 75% reduction in execution time 
(Note that in some instances, the memory usage of fixelcfestats may appear to drop drastically during permutation testing, e.g. from 50% to 4%; this is not cause for concern).