Git(*) is not a good tool for binary files. Unless you can somehow convert a world to an easily editable plain text format which Git can efficiently process, I'd say don't bother. Better look for some tool that can efficiently make a
"diff" of binary files (can't help you there, though).
Also, IIRC GitHub offers limited storage to free accounts, which rules out anything but the most basic world.
(*) Just in case, Git and GitHub are
not the same thing. Git is a source code management system, while GitHub is a site providing hosting for projects using Git.