Add `HekaStatsFilter` that converts `timer` and `counter` messages from a heka
client into StatPackets that are processed like statsd messages. Should ultimately
land in Heka itself, probably as a part of the `StatFilter`, but putting it here for now
so we can use it w/ Heka 0.2 behind the sync server.
Merge pull request #9 from mozilla-services/features/heka-stat-filter

Add `HekaStatsFilter` that converts `timer` and `counter` messages from ...