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

Hi all,

As requested I've updated 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>