Proposal to retire tmpnb.org in favor of mybinder.org

[MinRK]

tmpnb has had a great run! But keeping it up now is proving to be a bit of a problem. Most of the problems solved by tmpnb are now solved in a more sustainable way by the new Binder. We don’t currently have the support resources to keep tmpnb.org healthy.

My current proposal is to:

1. create a few binderable repos with the same goal of touring Jupyter features
2. update try.jupyter.org to redirect to one of these repos on mybinder.org instead of serving tmpnb.org in an IFrame
3. shutdown the tmpnb.org service

Issue for discussion

-Min

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