Added config to get the URL of the Redis server.
Put incoming bags into the right queue.

Also tweaked the API for the worker stub.
Put most of the S3 polling worker into place.

* Backing off from polling every minute to once a day;
* Reading configuration from the environment (and figaro) and
  `config/institutions.yml`;
* Connect to the various servers; and
* Poll each bucket and enqueue any tar files found.
Added a Rake task to run the S3 polling worker.
Added a Procfile to bootstrap the system.