Feature Request: health check endpoint

Would it be possible to create a route that provides some basic health check of the app?

For example: Atom worker running, elasticsearch running, memcached (if enabled), gearman (if enabled) are all running, and return a 200 OK and maybe a json response with OK's for everything, and if anything is down return a 503?

That way we can easily monitor from both a load balancer perspective, but also from our standard system checks!

Thanks for your consideration.

Start by locating the route entry point and the existing checks for the Atom worker, Elasticsearch, Memcached, and Gearman. Define how enabled and unavailable services should affect the response, then verify that the endpoint returns 200 with per-service OK results when healthy and 503 when a required check fails.

Written by the indexing model from the issue text.