Admin API

This release adds support for the Topic Admin API (KIP-4):

• Create and delete topics
• Increase topic partition count
• Read and modify broker and topic configuration
• Requires librdkafka >= v0.11.6

results, err := a.CreateTopics(
	ctx,
	// Multiple topics can be created simultaneously
	// by providing additional TopicSpecification structs here.
	[]kafka.TopicSpecification{{
		Topic:             "mynewtopic",
		NumPartitions:     20,
		ReplicationFactor: 3}})

More examples.

Fixes and enhancements

• Make sure plugins are set before other configuration options (#225, @dtheodor)
• Fix metadata memory leak
• Clone config before mutating it in NewProducer and NewConsumer (@vlad-alexandru-ionescu)
• Enable Error events to be emitted from librdkafka errors, e.g., ErrAllBrokersDown, et.al (#200)