initial attempt at using a single reply queue
factor out listener to share between srv_ctxs'
ack replies
tidy
tidy away internals behind api
consumers must (currently) all be added before any consumption starts
updated rpc tests
tidy up fixtures and fix test_errors
only need one of these
better consumer/connection test
flaking
Merge pull request #58 from onefinestay/single_reply_queue

single rpc reply queue