This is the initial deposit for `output-metrics` for Codahale Metrics.

This will satisfy #80 when completed.

*Do not merge yet* as this needs a bit of discussion around the resolution  for #91 which is also an issues with the ```AkkaIOStatsdCounterInterface```.

This is the initial deposit for ```output-metrics``` for Codahale Metrics (http://metrics.codahale.com) support. It follows the same general pattern of ```output-stats```.

As described in #91, I also looking for a bit of feedback on naming the metrics as Codahale is a bit more restrictive then those being sent to DataDog. An example of the current output for an actor system named *system* and prefix named *harness* would be as follows:

**System wide**
harness.actor-count

**System Actors**
harness.server.system.io-tcp.duration
harness.server.system.io-tcp.delivered
harness.server.system.io-tcp.delivered.bind

**User Actors**
harness.server.user.system.cluster.duration
harness.server.user.system.cluster.delivered
harness.server.user.system.cluster.delivered.leaderchanged