title: Django Tastypie always returning 401 unauthorized
body: <p>I'm using ajax requests to my tastypie resources, but even if I use SessionAuthentication() and DjangoAuthorization(), it gets always 401.</p>
  
  <p>resources.py</p>
  
  <pre><code>class EventsResource(ModelResource):
  
  user = fields.ForeignKey(UserResource, 'user')
  
      class Meta:
          queryset = Event.objects.all()
          resource_name = 'events'
          filtering = {'start': ALL,
                       'end':ALL
                       }
          list_allowed_methods = ['get', 'post','put', 'patch']
          detail_allowed_methods = ['get', 'post', 'put', 'delete']
          authentication = SessionAuthentication()
          authorization = Authorization()
          include_resource_uri = True
          limit = 0
          always_return_data = True
  </code></pre>
  
  <p>This is a resource for a calendar, so I have a Event Model, and my ajax requests are in a javascript file loaded in django-admin; I also checked if requests headers had csrf token and session id, but it doesn't work.</p>
  
  <pre><code>.ajax({
                      url:  event.resource_uri,
                      dataType: 'json',
                      contentType: 'application/json; encode=UTF-8',
                      type: 'DELETE',
                      success: function () {
                          $calendar.fullCalendar('removeEvents');
                          $calendar.fullCalendar('refetchEvents');
                          $('#modal-confirm').modal('hide');
                          showmsg('Evento eliminato correttamente', 'warning');
                      }
                  });
  </code></pre>