NF: added streamtube visualization mathod in fvtk
playing with colors and lighting properties
RF: started cleaning up the fvtk module. Removed unused functions and put all colors to be used for example with fvtk.colors.red rather than fvtk.red
DOC: on point glyphs
RF: renamed pretty_lines to streamtubes
DOC updated examples to use streamtubes
RF: simplified a tiny bit the slicer more work is needed
BF: data is now maskdata in the probabilistic example
BF: solving travis issue for when python vtk is not available
DOC: in dots and other cleanups
DOC: updated brain_extraction tutorial to render the picture correctly in the
website
RF: updated examples to show the odfs properly after cropped
Updated examples_index with some of the new examples
Removed axes from brain_extraction images
DOC: corrected figure name
DOC: Updated QB figure background
DOC: Modified EuDX angular parameter for better figures in example
Merge pull request #242 from Garyfallidis/pretty_lines

A new streamtube visualization method and different fixes and cleanups for the fvtk module