Adding optional healthcheck url for long-running tasks

If enabled, after restarting the container, ansible will wait for an
http healthcheck url to return a status code >= 200 and < 400
Updating healthcheck syntax and making retries NOT configurable

due to ansible bug https://github.com/ansible/ansible/issues/5865
Merge pull request #53 from modcloth/wait-on-healthcheck-after-deploy

Adding optional healthcheck url for long-running tasks