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.
More than you ever wanted to know about XML:

Namespaces were a failed idea from the late 90s and early 2000s, when standards were designed by committee without referencing how developers actually worked with web technology (ie: cutting and pasting sample code and hacking it). Some XML parsers throw a hissy fit when encountering namespaced tags with no declared `xmlns` or DTD, so best practice when providing custom XML documents is usually to avoid namespaces. The use case is 

Other thing to consider is that if we invent custom FOASS tags, they could be polymer/web components as well, so any non namespaced tags used here could also be reused in the HTML. Goes the other way too — using `<h1>` and `<p>` tags in the XML would be easy to parse and unambiguous.

If you want to leave this as-is, I’ll take a look at improving the markup once this PR is merged.