Outdated stable branch and malfunctional mybinder.org badge

[consideRatio]

Visiting this repos mybinder example, both using the old stable branch as in the README, or the current master branch, gives us:

This is because mybinder.org won't automatically realize it should install the jupyterlab extension. We would need an apt.txt file in the repo for that to happen where we write:

jupyter labextension install @jupyter-widgets/jupyterlab-manager
jupyter labextension install jupyter-matplotlib

Also, update the readme to use the master branch may be simpler than remembering to update the stable branch?

[martinRenou]

Thanks for the report. Would you mind opening a PR for the jupyterlab build?

The reason for the stable branch is that if the master branch moves too much, users don't need to rebuild the docker image on binder