chore(requirements): update jsonfield to 2.0.0

See rpkilby/jsonfield@1.0.3...2.0.0

Author: mboersma

rootfs/requirements.txt

@@ -9,7 +9,7 @@ docker-py==1.10.6
 gunicorn==19.6.0
 idna==2.4
 jmespath==0.9.1
-jsonfield==1.0.3
+jsonfield==2.0.0
 jsonschema==2.6.0
 morph==0.1.2
 ndg-httpsclient==0.4.2