Ack failed messages
Concurrency is now a channel_option
Parsing json _could_ cause an exception
only ack and reject in the ensure block. this way we avoid failing to ack/reject in a rescue because something raises in the rescue. we hope this stops queues from backlogging
A connection per process and a channel per thread
reconnect needs to clear things out
Bump version to 0.6.0
Merge branch 'ack-failed-messages'

Conflicts:
	lib/watership/version.rb