High level consumer with non-blocking feature

[aNutForAJarOfTuna]

A high level consumer based on the original consumer

Implemented:

• Allow client to take n messages at a time without blocking even not enough message in kafka
• Auto commit offsets for consumed messages, not commit on failure.

  TODO:

• Multiple consumers in the same group consuming at the same time without duplicated message.

[Jroland]

Thanks Nut, ill have a look this week. Might be a good idea to create multiple high level consumers packages that build on the base.

[altruism]

@Jroland any news on this PR?