Count Aggregator about stackexchange.metrics

[bretcope]

I've pushed that 90% work onto a branch now with commit 9969040

There seems to be some other issues with by local Bosun, so I'm not entirely convinced there is actually any issue with the code. I'll try it out when I get back from vacation and have more than just my laptop.

[bretcope]

This issue turned out to be a race condition in my test program where shutdown was called within one second of the last snapshot, causing multiple data points to report as the same timestamp. I switched the timestamp to report as milliseconds, which, for all practical purposes, should eliminate this race condition.

The count branch is now merged into master.