Add `roborev install-hook uninstall` to uninstall the hook

[criccomini]

I prefer to run the revs manually. It seems I installed it by accident. I'd like to easily uninstall it from the roborev cli.

[wesm]

I think you can just run roborev enqueue without having run roborev init, I'll clarify this in the README but also add an uninstall-hook command

[wesm]

done in f079ce2