[MODEL] [TEST] Removed hardcoded port 9250 and used ENV['TEST_CLUSTER_PORT'] in test cluster initialization
[RAILS] Updated the dependencies for `elasticsearch-rails`

* Load -model from disk if available
* Remove coveralls (breaks with Rails, useless anyway)
[RAILS] Added test helper for `elasticsearch-rails`
WIP > ActiveSupport::Instrumentation support for Elasticsearch

See: http://edgeguides.rubyonrails.org/active_support_instrumentation.html

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TODO:

* Publish "Model Search RESPONSE" event (took, number of results, etc.)