Add support to publish RAW alert to rabbitmq

It would be really nice to add a new Alert output node to rabbitmq.

I made a python scripts I called with the exec script, but it feels dirty. I am not familiar with Go so I don't really know how to write an ouput node for kapacitor.

The params needed for this type of alert would be:
- A valid rabbitmq URI (https://www.rabbitmq.com/uri-spec.html)
- exchange
- routing key

No files or tests are named. Start by locating the existing alert output nodes and how the exec script receives alert data, then review RabbitMQ's URI specification. Done means a RabbitMQ alert output node can publish the RAW alert using a valid URI, exchange, and routing key, with coverage for the new parameters.

Written by the indexing model from the issue text.