WHITESPAAAAAAAAAAACE
Add bear as a dependency

bear has a much better thought-out approach to computing statistics,
and also computes a hell of a lot more of them than estatsd currently
does.  We can use this to get a lot more info out of our metrics.
Use bear to compute mean

Earlier, we were only computing the mean of everything below the 90th
percentile!
Use bear to compute min
Use bear to compute max
Use bear to compute count
Use bear to compute 90th percentile
Cleanup, reorganization
Add percentile/2 helper function
Consolidate metric extraction with reported_metrics/1
Add 95th and 99th percentiles
Add 50th percentile (median) to reported statistics.

Medians are fun.
Use median rather than 50th percentile for easy discovery.
Update rebar.config.lock