Initial commit of badge model

This contains a slightly (though increasingly as time goes on) customized version of the django-roa module, used to allow Django models to be represeted on a remote REST API.  (In this case, badgekit api)
This feels like it would make more sense to accept `key` and `secret` parameters, rather than being tied explicitly to the config. Of course, it's a somewhat redundant point given you're calling it immediately below, but it feels more pythonic somehow.