Add back the favicon to avoid routing errors
Validate presence of user's token
Update readme
Update the Waffle badge to show the backlog
Update ActiveModel::Serializers to 0.9
Implement a regular session-based authentication

If we're on the same domain (and client *will* be on the same domain as
the server), then we can just use regular Devise's authentication
through sessions (no tokens). This solves any potential security fixes
(e.g. session hijacking).

Fixes #11
Fixes #7