chore(requirements): update django-guardian to 1.4.4

See https://github.com/django-guardian/django-guardian/blob/devel/CHANGES
and django-guardian/django-guardian@v1.4.1...v1.4.4

Author: mboersma

rootfs/requirements.txt

@@ -2,7 +2,7 @@
 #
 Django==1.9.5
 django-cors-headers==1.1.0
-django-guardian==1.4.1
+django-guardian==1.4.4
 djangorestframework==3.3.3
 docker-py==1.8.0
 gunicorn==19.4.5