Added Kibana-friendly Elasticsearch reporters.

Added reporters for Elasticsearch. Reporting can be done using the HTTP or Transport APIs. As such, the modules are split into metrics-elasticsearch-http and metrics-elasticsearch-transport with a common metrics-elasticsearch module that they both depend on.

Metrics report in a format similar to Logstash so that Kibana dashboards can be easily created.

Included integration tests with Elasticsearch.
whitespace police