Allow different services to be run on different server roles

[tomafro]

The recipes have only been tested using a single server for all roles. A more complex deployment might be the web server on one machine, and the job queue processors on another.

[lazyatom]

Do you know that this doesn't already work?

[tomafro]

Not sure how it can work, as there's only one Procfile shared between all machines. If it does work, then bingo, issue solved!

[lazyatom]

Ah, I forgot about the Procfile :)