Merge pull request #40 from erikcw/master

Change user.is_authenticated check for Django 2.0

pinax/referrals/models.py

@@ -100,7 +100,7 @@ def record_response(cls, request, action_string, target=None):
 
     @classmethod
     def referral_for_request(cls, request):
-        if request.user.is_authenticated():
+        if request.user.is_authenticated:
             qs = ReferralResponse.objects.filter(user=request.user)
         else:
             qs = ReferralResponse.objects.filter(session_key=request.session.session_key)