Sqs

quick hacks to fix the from SQS block. Needs work in the future - maybe waitgroups and a fixed number (> 1) of readers would be nice instead of this clumsy locking an unlocking. Also adds a 1second wait time to block the reader for a second at a time if there are no messages on the queue. This means max additional latency for slow streams on SQS will be 1 sec.