Exclusive consumer And FuturePublishAsync

Hi!

It's an implementation of exclusive consumer.

Unfortunately, RabbitMQ has no such functionality like this http://activemq.apache.org/exclusive-consumer/, but I think it's really usable. 

So, now, if you try to twicely subscribe with exclusive flag, one of subcriptions will die with exception(but in easynetq - just error in log!).

How you think, is it possible to emulate such functionality in easynetq? I mean awaiting of successful subscription when the eclusive flag is set. We have an example of this scenario, when we publish to external system(billing) and we really care about ordering(if order will break, somebody can pay with wrong requisited) and failover(if consumer will die, nobody can pay for service).