Create "Submit for Review" functionality

[zleyyij]

This functionality would look like this:
Instead of saving changes, user would hit a button that would "submit for review"
This would create a new branch with the changes, push to github, then open a PR, possibly with a user provided description.

At some later point it might be cool to have a dashboard in the editor for individuals with write perms to approve changes in the dashboard, but that's a larger feature, so might be best suited for another time.