Update djangorestframework for better 1.7 support

requirements/prod.txt

@@ -32,7 +32,7 @@ django-mysql-pymysql==0.1
 django-post-request-task==0.0.3
 django-quieter-formset==0.4
 django-raven-heka==0.3
-djangorestframework==2.3.12
+djangorestframework==2.4.8
 djangorestframework-jwt==1.7.2
 django-statsd-mozilla==0.3.10
 django-storages==1.1.8