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.
@maetl you're right, it's deliberately over complicated - what better way to wrap a "fuck you" than in "fuck you" XML :).

I think that the xml namespace declaration is valid here (`<foaas:response xmlns:foaas="http://foaas.com/fuckoff">`), if more verbose than it needs to be.

I've found an XML escaping library on NPM which looks like it will do the job: https://www.npmjs.com/package/xml-escape.