Initial API Design

This is not the completed TimePulse API. However it's the basic skeleton on which I'm going to build the other endpoints, so I'd like someone to look at it before I do so.

Basic features are:
1. Oauth2 for authorization
    a. Client requests access token with user/password + client id/secret at /oauth/tokens (or with refresh token)
    b. Client passes access token in http headers to any protected route.
    c. Protected routes simply return 401 if not authorized with no content.
2. Active Model Serializers for serialization.
4. Index actions can also be passed an array of ids
5. Haven't done paging or query params yet.