chore(requirements): update pytz to 2016.4

Author: mboersma

rootfs/requirements.txt

@@ -11,7 +11,7 @@ morph==0.1.2
 ndg-httpsclient==0.4.0
 psycopg2==2.6.1
 pyOpenSSL==16.0.0
-pytz==2016.3
+pytz==2016.4
 PyYAML==3.11
 requests==2.9.1
 requests-toolbelt==0.6.0