Proposal: Move clusters tab to ipyparallel

[minrk]

I think we should ship it as a notebook server extension in ipyparallel, rather than keep it in the notebook code.

[takluyver]

It would be good to have this as an internal validation of the server extension machinery.

[damianavila]

I think we should ship it as a notebook server extension in ipyparallel, rather than keep it in the notebook code.

I agree.