Syncs up with Heroku's platform API schema and HTTP API Design Guide

* Makes sure to use the interagent meta-schema as the current Heroku's platform API does.
* Adds `stability` and `strictProperties` to resource schemas
* Fixes `identity` property so that it follows the HTTP API Design Guide
* Re-orders properties to make schemas more readable for humans.

Hopefully this will close #186 and #185. All tests are passing.
I'm not sure how generically we can (or should) apply this. There are many things were this works and can be nice, but others where only the id is really sensible (or the alternative is something other than name). I'm not saying we should preclude it or anything, but I guess I am reticent to have it as a default. What do you think?