I actually like having separate commits. I think it's pretty descriptive. Still, looking at the rebase "interface" now (ran `git rebase -i HEAD~4`) it would seem doable.

What I'm gonna try instead is add a fifth commit with some fixes to the readme, then "squash" that with the fourth. That is a somewhat  difficult way to do it compared to amend (which I'm a happy user of, through Tower.app) but it might prove to be my first successful encounter with rebase.