ENH: Add option to write binary tensor files

Implemented writing out figer track VTK files in the
VTK binary format.  Added a test to compare a binary
file with the supposedly identical text file.

In the process added a dependency on VTK, in order
to use VTK readers in the file comparison program used
in testing.
COMP: Replace baseline vtk image

2T_fw_fiber.vtk baseline doesn't match current output.
I assume users think UKF is working correctly, and some
small algorithmic change is causing the mismatch
Merge pull request #1 from Chaircrusher/WriteBinary

ENH: Add option to write binary tensor files