BUG: Corrected name of kurtosis file produced by dtifit

See merge request fsl/fslpy!77

Bf/imcp paths

See merge request fsl/fslpy!78

It's called kurt rather than MK

Doc/filetree

See merge request fsl/fslpy!76

Added filetree to fslpy

See merge request fsl/fslpy!69

reverting back

needed for python 3.5

Mnt/drop py2734

See merge request fsl/fslpy!75

work to do here

this is all handled by nibabel. Also never keeps its own ref to file object.
Image.save always saves to a temp file, then moves that to the destination -
avoid any problems with mmap/indexed_gzip.