Change Activity Graph from Protovis to d3 (#43)

Fixes failing javascipt in Opera and Chrome resulting
in no graph and no other javascript features.

Changed to precalculate all days in the begin_date...end_date
date range before matching email counts to ensure we have data
points for all days in the range.


*Note*
This is not the prettiest graph the world has ever seen, but at least it displays in all browsers.  A small step for a hyper kitten :)