G2nb

* Added the ability to toggle the rich text editor on or off, to access native Jupyter editor functinality

* Bug fix for erroneous change to code cell type

* Upgraded rich text library to TinyMCE 5
* Added "Rich Text" pseudo-cell type

* Updated PyPI deploy to latest standard

* Updated conda packaging
* Updated numbering scheme

* Fixed display issues when viewing in Safari
* Updated build config for latest versions of webpack
* Turned off navbar by default
* Fixed multiple rendering bug