feature: HipHopCommunitySettings on user

Closes #1 (closed)

serialized on the user model like so:

{
  // ...
  "hiphopSettings":{"@id":"http://localhost:8000/hiphopusersettingss/1/","choice":"test-choice","user":{"@context":{"get_full_name":"rdfs:label"},"@type":"foaf:user","@id":"http://localhost:8000/users/admin/"}
}