Create a version of the stack with many brokers

[jzweifel]

Right now the stack we build includes a single broker. This is great for quickly spinning up a sandbox in which to play with Kafka.

However, some more interesting scenarios can be tested in a multi-broker stack, and additionally most production deployments of Kafka will have multiple brokers, so it would be good to have a version of the stack that includes multiple brokers.

• create another version of the waffle stack that has 3 kafka brokers set up in a cluster