support auto creating a topic if it doesn't exist

[SingingBush]

When integrating with Kafka using Spring Framework it's easy to get a producer/consumer running without needing to configure anything and when running a producer, if the topic doesn't already exist, Spring will just create it. It's also configurable via auto.create.topics.enable which defaults to true.

It would be great if kafka-d could do the same as it really simplifies deploying a new producer