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.
Merge pull request #2 from aslakknutsen/graph

Change Activity Graph from Protovis to d3 (#43)