Major release branches

[kenns29]

Taking inspiration from deck.gl, we need to have some major release branches, e.g.

This is necessary for us to maintain those releases. Because we also have a major Jupyter binding, we can have two lines releases for the major packages and the Python libraries.

release-1.0.0 
...
release-jupyter-0.1.0
...

Patches to these releases use the minor version number, e.g.

release-1.0.1
release-jupyter-0.1.1

[Firenze11]

Good idea, let's do this starting from future releases. I copied the idea into https://github.com/uber/manifold/blob/master/CONTRIBUTING.md and closing this issue.