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)
Oh, I'm not suggesting that it shouldn't be overridable, just that the default value could be picked up from information already available. Might also make sense to stick the information in the `Meta` subclass, rather than directly on the model, regardless of what you end up doing.

```python
class Badge (ROAModel):
    class Meta:
        remote_field_name: 'badge'
        remote_field_name_plural: 'badges'
```

Ideally I suppose `remote_field_name` would default to either `db_table` or `verbose_name`, and then `remote_field_name_plural` would default to the pluralized version of that (in the same way that `verbose_name_plural` does with `verbose_name`).