Render fonts correctly in SVG graphs

@robyoung
@pbadenski
Add fonts directory for .ttf NTA.
Rearrange functions to avoid scoping issue

page.evaluate executes the function in the context of the page rather than the PhantomJS script.

@pbadenski
@robyoung
Render NTA fonts on the graph images

NTA tabular numbers do not work yet, standard nta font is used for everything.

@norm
@pbadenski