This change allows the `-o <initials>` flag to override who the main
author of any commits in this repo will be going forward.
What this actually does, is that it modifies the Repository's config
file to change the `user.name` and `user.email` like this.
Running `git mob -o ae be` (given the corresponding authors have been
configured using `git add-coauthor`) is equivalent to doing:
git config user.name "Alice Example"
git config user.email "alice@example.com"
git mob be # be being the initials of "Bob Example" <bob@example.com>
Martin Frost