Lookup Kafka brokers from Zookeeper

Create a new ```Herman::Providers::JavaProducer``` object with the zookeeper info instead of broker ids.

This removes the functionality of instantiating the JavaProducer object with broker ids.
This method will return garbage data if `hash` is an empty hash, it will return something like `":"`


I think that error case should be covered and the error condition for the method should be to return a `nil` so that L48, the response from `#fetch_brokers` can be `brokers.compact` to purge nil values