Just found TuneMachine on Hacker News.
This project was made by the ScottyLabs' team, consisting of Oscar Bezi, Justin Gallagher, Min Zhou, and Jake Zimmerman at a16z's Battle of the Hacks v2 in June 2015.
See it live at http://tunemachine.herokuapp.com.
TuneMachine lets you take snapshots of your Spotify playlists and restore to a specific version at any time. It has a super simple interface. Once you log in, you see all of your playlists. From here, you can see a list of snapshots you've taken of each playlist, and for each snapshot you can see a quick overview of what the playlist looked like at that point in time. This makes it super useful for keeping track of what's changed over time inside collaborative playlists.
Tribe Games