This application is a simple "TODO" list API. Users interact with the API using API key/id pairs. Users sign up using a simple process via the Stormpath API. The Express-Stormpath NPM module handles all of the user sign-in, registration and authentication processes, alleviating the user of the responsibilities of creating, storing and authenticating users.
In order to use Stormpath, you must sign up to use their API. This will give you an API Key file. Use this in the application, or use environment variables to pass in the id/secret (as I have done in stormpath.init).
TODO API heavily influenced by Adrian Mejia's Creating RESTful APIs With NodeJS and MongoDB