Fixes for the doSyncNs method:

 - ack messages when throwing exception so the temp queues don't
   stick around
 - delete temporary queues when they are no longer needed. This means on
   long running applications that keep a connection open we don't end up
   with stale temp queues sticking around.
Round 2 of fixing the doSyncNs method.

 * don't throw exceptions from the callback
 * reopen a new channel if the channel gets disconnected because of an
   error.
 * remove auto-delete flag that is not needed now that we don't throw
   exceptions in the callback.
 * remove ttl setting that is not needed now that we don't throw
   exceptions in the callback.
 * Add helpful comments to code.
Merge pull request #106 from gauthierm/amqp-module-sync-fixes

Fixes for the doSyncNs method: