Green for valid, red for invalid on SVG for iPython notebook

As requested update the SVG colours to green for valid and red for invalid. I've updated the example [here 
(http://nbviewer.ipython.org/gist/om-henners/10006338)](http://nbviewer.ipython.org/gist/om-henners/10006338).

Signed-off-by: Henry Walshaw <henry.walshaw@gmail.com>