Added experimental file for filtering streamlines
Merge pull request #22 from StongeEtienne/new_fvtk

New fvtk streamlines visualization
Merge branch 'new_fvtk' of github.com:Garyfallidis/dipy into new_fvtk
New file for vtkWidgets addes slide_widget function
Adding button widget still work in progress
Updated filter_streamlines still wip
New file named guillotine added
Implemented a working slicer
Refactored guillotine in a class
Added Numpy -> vtkImageData conversion
Changed add_data_volume default opacity
Corrected axis orientation for image space visualization
Updated TODO list
Updated fvtk_widgets
Clean up guillotine.py
Fixed bug with NAN in volume data
Added support of world coordinate system
Added Key actions and proper documentation
Refactored code, added snapshot feature and display methods
Finished documentation and added some display functions