cassandra output plugin

We've created a new version of the old cassandra output plugin
It is slightly more robust, has full coverage, and uses the Logstash 2.x APIs
How can we move forward with including it in the general logstash plugin repo?

p.s.
It is available as [a gem on rubygems](https://rubygems.org/gems/logstash-output-cassandra) and [the code](https://github.com/PerimeterX/logstash-output-cassandra) is also available on github

Start by reviewing the linked logstash-output-cassandra gem and GitHub repository, then compare them with the Logstash plugin repository's documented inclusion process. The issue does not name a target file, test, entry point, or acceptance criteria, so the next step is to establish those requirements before work can be considered done.

Written by the indexing model from the issue text.