FuturePublish based on rabbitmq dead lettering

Hi guys!

Here is an implementation of future publish on pure rabbitmq.

I'm not sure about naming, may be it was not so good idea to name the method with timespan argument as future publish, but I have no ideas about that.

Also, this solution creates extra exchange and extra queue for pair of message type and offset. Si, It's a bit ugly, but I haven't found something better.