WIP > ActiveSupport::Instrumentation support for Elasticsearch

"Tested on humans"

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

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TODO:

* Tests
* Documentation

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NOTES:

https://github.com/rails/rails/blob/master/activerecord/test/cases/log_subscriber_test.rb
https://github.com/rails/rails/blob/master/actionpack/test/controller/log_subscriber_test.rb
https://github.com/rails/rails/blob/master/actionview/test/template/log_subscriber_test.rb