When a new rollout with a different size than the previous size of the
deployment is initiated then only the new replica set will notice the
new size. Old replica sets are not updated by the rollout path.
Changes:
* moved waiting for synced caches before starting any work
* refactored worker() to really quit on quit
* changed queue to a ratelimiting queue and added retries on errors
* deep-copy deployments before mutating - we still need to deep-copy
replica sets and pods
* rolling.go (has all the logic for rolling deployments)
* recreate.go (has all the logic for recreate deployments)
* sync.go (has all the logic for getting and scaling replica sets)
* rollback.go (has all the logic for rolling back a deployment)
* util.go (contains all the utilities used throughout the controller)
Leave back at deployment_controller.go all the necessary bits for
creating, setting up, and running the controller loop.
Also add package documentation.
