Badge awards

This adds badge awards, and modifies ROA to allow for more dynamic resource URL construction (to allow awards to be fetched by badge and by user)
This feels like it's something that could be refactored out a bit...

```python
BADGEKIT_ROOT = urljoin(settings.BADGEKIT_API_ENDPOINT, '/systems/%s/' % settings.BADGEKIT_API_SYSTEM)

def badgekit_url(path=None, *args, **kwargs):
  if path is None:
    return BADGEKIT_ROOT
  return urljoin(BADGEKIT_ROOT, str(path).lstrip('/').format(*args, **kwargs))
```

...which would allow you to do something like this:

```python
return badgekit_url('/badges/{badge}/instances', **kwargs)
return badgekit_url('/instances/{0}/', person.email)
```