added Dygraph rendering of Graphite data

[bhenerey]

Hi,
I've added an initial javascript library to get Graphite JSON data and render it in a div with Dygraph. This allows interactive graphs (Zooming, etc), instead of static graphs.

• It will graph multiple standard data series.
• Additional Graphite API functions (http://graphite.readthedocs.org/en/1.0/functions.html) are not implemented.
• The json is parsed into Dygraph format and the graphs are rendered client-side, so lots of data will be slow....

Thanks,
Brian Henerey