Refactor everything.

Loads of changes:

* Complete refactor/restructure.
* Renderers now autoload from `/renderers` dir, one file per renderer.
* `Accepts` / `Content-Type` now dynamic from above.
* Operations similar from `/operations` dir, one per operation. 
* `/operations` resource now dynamic from above.
* Express app now in FOAAS class, separate from server. FOAAS contains own version number.
* Specs for renderers/operations.
This seems overly complicated for what it does—perhaps deliberately so?

There’s an undeclared namespace (no `xmlns=""` attribute on the document) with a tag vocabulary that seems influenced by SOAP, but throws in a troll-ish `subtitle` element just to be special.