requested to merge sgilles/gettingstartedwithmoderncpp:jupyter_extensions into master
As we rolled back to vanilla Jupyter:
- Fix the README which kept suggesting to use
- Add in the environment the jupyter_contrib_nbextensions module
- In README, indicate how to activate two of them to enable table of content updating and Bibtex proper rendering.
The table of contents for notebook 1-4 has been updated properly.