moved module to use `graceland-metrics-` prefix.
Merge branch 'feature/host-aware-graphite-reporter' into develop

* feature/host-aware-graphite-reporter:
  moved module to use `graceland-metrics-` prefix.
  can replace host multiple times.
  reporter factory throws an exception if given misformatted prefix.
  fixed double dots when host is not available.
  added the reporter factory to `META-INF` so it's found by the `ServiceLoader`.
  added underscore replacement for non alphanumerics.
  added powermock to mock the hostname returned for testing.
  added host aware graphite reporter factory with host aware `getPrefix()`.
  added graphite sub-module.