Fix for compat for ipywidgets and ipynb#196

bnouvelbmll wants to merge 3 commits intojupyter:mainjupyter/jupyter-sphinx:mainfrom

bnouvelbmll:fix-compat-for-ipywidget-states-and-mystnbbnouvelbmll/jupyter-sphinx:fix-compat-for-ipywidget-states-and-mystnbCopy head branch name to clipboard