Change clustering guide to assume production/multi-machine configuration

[bruth]

The current guide demonstrates how to run a cluster on a single host. This is useful to quickly get a cluster running to understand how the configuration works, however it doesn't provide guidance or the mental model for production concerns.

List of possible improvements:

• Add diagram to show the routes and then full mesh behavior
• Define prerequisites/considerations for a production deployment
• Use example hostnames throughout the guide assuming three machines have been provisioned, e.g. n1.us-east.example:4222 n2.us-east.example:4222, and n3.us-east.example:4222