Allow 'url' key in general, but delete it for reprocessed scripts.
Because of nested merge, removing 'url' must be done last.
Merge pull request #47 from plotly/andrew-fix-model-urls

Andrew fix model urls
Merge branch 'master' into 3d-again
re-processed random-walk simple-3d-scatter elevations-3d-surface
Ran publish.py test, then publish. Excluded new js.json reference.