Broken commit, switching to response object
Broken - Fixes for unit testing
Return everything back to the controller

Each {model}API file was using die() with the appropriate HTTP response
code to indicate error status. This made unit testing difficult so now
everything is pushed back to the controller where it is encoded to JSON
and echoed.
Unit tests for Contract, Invitation, and Model API

Create unit tests for ContractAPI, InvitationAPI, and ModelAPI.
New SubscriptionAPI unit tests
Create methods to manipulate podcasts

Also create unit tests and functional tests for these operations.