Similar project: scuttlebutt

I found [this project](https://github.com/dominictarr/scuttlebutt) and their [collaborative text editing](https://github.com/dominictarr/r-edit) uses similar ideas to ConcurrenTree. See the [paper](hal.inria.fr/docs/00/44/59/75/PDF/icdcs09-treedoc.pdf).
