Use open source flot for graphing sparklines instead of Google Chart black box

this issue is for the purpose of settling on a final charting solution for this module, as it will be the one we use with sampler api to generate all of our metrics sparklines for the redesign.

options:

1. third party solution, currently google chart api. over at #428680: Change usage stats to not use google charts it's been taking some heat for being a black box solution, which we try to avoid on drupal.org.
2. in house solutions
   1. client-side, like flot module. this will reduce the usage of our server resources, but would not work in all cases as the client has to support whatever we're using. flot uses javascript, which is pretty ubiquitous in the 2010 browser world
   2. server-side, probably some kind of system where we generate sparkline images, cache them, and send them over the wire. would eliminate client-side inconsistencies, but would put more burden on our processor power, storage, and bandwith.

i vote for b.1.

i'd like to get this resolved asap, as our goal is to have some metrics go live for the next sprint demo.