Implement a more dynamic celery queue system

* Meant to be a starting point to more efficiently manage work routing
  and to balance work across all tower nodes
* Integrate flower as a dev tool that starts alongside other nodes.
  Helpful for observing and monitoring the queues/exchanges
* For the moment, force the task manager to only run on one node (not
  sure if this is needed)
* Define queues and routes for all task work
* Bump celery version to 3.1.23
* Expose flower through haproxy

tools/docker-compose-cluster.yml

@@ -11,6 +11,7 @@ services:
     ports:
       - "8013:8013"
       - "1936:1936"
+      - "5555:5555"
   tower_1:
     image: gcr.io/ansible-tower-engineering/tower_devel:${TAG}
     hostname: tower_1