@progrium suggested to follow the variables that docker --link uses. This currently isn't done. It is a good idea, but apart from the ${name}_PORT variable, all the others include the actual port number, which would mean parsing the value returned from discoverd. 

Part of what I am struggling with here is that I see myself using symbols in the service names. I want to differentiate between ``app1:db`` and ``app2:db``. So you can't just uppercase it to convert it to an env var.