chore(requirements): update to docker-py 1.9.0

https://github.com/docker/docker-py/blob/master/docs/change_log.md#190

Author: helgi

rootfs/requirements.txt

@@ -4,7 +4,7 @@ Django==1.9.8
 django-cors-headers==1.1.0
 django-guardian==1.4.4
 djangorestframework==3.4.0
-docker-py==1.8.1
+docker-py==1.9.0
 gunicorn==19.6.0
 jsonfield==1.0.3
 morph==0.1.2