feat(metrics): Add github.com/rcrowley/go-metrics
feat(metrics): Add metrics pkg
feat(metrics): Add documentation and contrib scripts
feat(metrics): enable some metrics; push to graphite

* -trace flag controls whether or not to enable metrics-gathering
  and the /debug/* HTTP endpoints
* -graphite-host flag controls where metrics should be sent
* timer.ae.handle metric tracks execution time of AppendEntriesRequest
test(store_bench_test.go) add watch bench
Merge pull request #493 from xiangli-cmu/bench_watcher

test(store_bench_test.go) add watch bench
bump(github.com/coreos/raft): bf7accb84ce4fe446983abffe00dd18a6b8cbc18
feat(metrics): Publish peer heartbeat events as metrics
test(ci): Replace travis.ci with drone.io
Merge pull request #496 from bcwaldon/droneio

test(ci): Replace travis.ci with drone.io
Merge pull request #483 from bcwaldon/metrics

Integrate go-metrics
fix(store): properly hide hidden keys from watchers, not just gets
fix(store): move logic to handle whether or not to notify (re: hidden keys) entirely into watcher hub
test(store): exercise watchers receiving notifications of non-hidden keys within hidden directories
fix(store): make isHidden see if any portion of the path is hidden, not just the last element
test(store): group together all store tests that deal with hidden keys
Merge pull request #498 from tobz/actually-hidden-keys

fix(store): properly hide hidden keys from watchers, not just gets
adding .net client
Merge pull request #499 from drusellers/patch-1

adding .net client