Fixed compatibility issue with dipy 0.7.
Revision according to the refactoring
Fixed issue of 'length' import.
Merge pull request #2 from Paolopost/dipy07

Fixed compatibility issue with dipy 0.7.
Color_FA with trackvis data structue is also computed
Fixed extension of dipy tratography file
Naming of Color_FAs changed
Merge pull request #3 from dporro/color_FA-tra

Color_FA with trackvis data structure is also computed