Pass multi message to handler using batchSize #165

Is your feature request related to a problem? Please describe.
For now we're able to fetch multi messages using batchSize, and single message will be passed to executor.

Describe the solution you'd like
We want a new feature to passing the batched messages to executor. In other words, we want to execute like below.

@RqueueListener(value = ["email-queue"], concurrency="1", batchSize = "3")
fun handleEmailMessage(messages: Collection<GenericMessage<Any>>) {
  println("received email message: $messages")
}

I appreciate if you let me know a way with current implementation or any thought about my request.