chore(requirements): update psycopg2 to 2.7

See http://pythonhosted.org/psycopg2/news.html#what-s-new-in-psycopg-2-7

Author: mboersma

rootfs/requirements.txt

@@ -14,7 +14,7 @@ jsonschema==2.6.0
 morph==0.1.2
 ndg-httpsclient==0.4.2
 packaging==16.8
-psycopg2==2.6.2
+psycopg2==2.7
 pyldap==2.4.28
 pyOpenSSL==16.2.0
 pytz==2016.10