[Branching] Branch the Jepsen repository

What's the problem?

We need to branch the Jepsen repository to isolate new changes being made to the repository.

What's the fix?

We could adopt a subset of the git-flow workflow:

https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow

Create a develop branch from master.

Let master be the abridged final release branch which is tagged.

Use the develop branch for development, merge into master upon release.