Collection roles and preferences

Just wondering if you saw the yield i added to turn this into a block: https://github.com/zooniverse/Panoptes/blob/d6d6317759bc4996d0c1bcf825d2a6a22f6c9aaf/lib/json_api_controller/creatable_resource.rb#L24

e.g: 
```ruby
super(create_params) do |create_params, link_params|
  link_params[:user] = api_user.user
  create_params[:user_ip] = request_ip
end
```