chore(controller): update djangorestframework to 2.4.4

See http://www.django-rest-framework.org/topics/release-notes#24x-series
and encode/django-rest-framework@2.4.3...2.4.4

Author: mboersma

requirements.txt

@@ -9,7 +9,7 @@ git+https://github.com/deis/django-fsm@propagate-false
 django-cors-headers==0.13
 django-guardian==1.2.4
 django-json-field==0.5.7
-djangorestframework==2.4.3
+djangorestframework==2.4.4
 docker-py==0.4.0
 gunicorn==19.1.1
 paramiko==1.14.1