This code currently fails.

This is because of some silly bugs in dti.py. Going next to fix that.
BF: Use `iterable` to determine if sigma is a sequence.
Merge pull request #222 from arokem/fix_restore_bug

BF - Fix restore.
Fix make examples for windows.
Merge pull request #223 from matthieudumont/fix_makeexamples_windows

Fix make examples for windows.
Merge pull request #212 from Garyfallidis/fvtk_ellipsoid

NF+BF - Tensor visualization.
NF: added streamtube visualization mathod in fvtk