fix: FSL FNIRT intensity mapping files#1799

Merged

satra merged 6 commits intonipy:masterfrom

cgc:intmap_ext

Feb 8, 2017

Commits on Feb 4, 2017

Commits on Feb 6, 2017

Address PR comment by making sure exists=True is kwarg for File
cgc
committed

Commits on Feb 7, 2017