Cleanup imports

accounts/models.py

 from django.db import models
-from django.contrib.auth.signals import user_logged_in
 from django.dispatch import receiver
 from django.contrib.auth.models import User
 from django.conf import settings
-from django.db.models.signals import post_save, pre_save
+from django.contrib.auth.signals import user_logged_in
+from django.db.models.signals import post_save
 from django.utils.translation import ugettext_lazy as _
 
 from lang.models import Language