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.
These tests are extremely brittle, with the full HTML document (whitespace and all) being asserted as a full result. in future, a string assertion or tag/regex match might be easier to work with—or else a capturing variable/const rather than the inline string.