Add option to set the fontsize in a graph

Hey Russ,

I'd like to add the fontSize option (http://graphite.readthedocs.org/en/1.0/url-api.html#fontsize) to graphview. Could be useful for those of us with lesser eyesight! :)

Specifying the areaMode (http://graphite.wikidot.com/url-api-reference) can be useful for multiple targets.

Also, specifying the color list as per the colorList parameter (https://graphite.readthedocs.org/en/latest/render_api.html#colorlist) might also come in handy to those who have default colors not suitable for multiple targets.
A better implementation in my opinion would allow the specification of a color for each target (e.g. "series": [{"target": "stats.target_timer", "color": "red"}], but this would require access to the graphite config as I'd like to use the default color values when a color is not specified for a target. I might think some more about this when I have some more time.

Cheers,
-Alex