pep8
removed NaN checking
mv utils.py to helpers.py ; mv function from roi.py in new utils.py
added utils.py
added doc string for helpers
added fit method to parcellation
improved parcellation.inverse_transform
swapped fit arguments
fix parc
Parcellation.r_masks_ are now in the image space
Fix bug from https://github.com/schwarty/regions/pull/1
BF: Fix various bugs.