[WIP] Add rough draft of public API

Hi Max,

I submit for your approval a rough draft of a RESTful API. If I'm missing anything (including the big picture!), let me know. We can use this pull request to refine the spec.

The API is documented using [RAML](http://raml.org) a YAML-based language for describing RESTful APIs.

RAML encourages reuse of resources, so the brunt of the documentation is contained in the root `resourceTypes` hash.

There are several tools available to render RAML in more accessible formats. I've bundled an example generated using [raml2html](https://github.com/kevinrenskers/raml2html).

**Note:** I've purposely excluded example requests and responses until the models are well-defined.