Supertux Editor Installation Help

Hello, I just finished playing through all of the add-ons, old levels, etc. in the newest version of supertux, and I decided I'd get back into the level editor, since it had been a while. However, I quickly discovered that installing the editor had grown much more complex on Linux than it has been before. The instructions tell me to compile the editor from github, but when I do that, I get an error saying the repository doesn't exist. Over the past week, I've looked for a way to compile, install, download, run, etc. the newest version of the editor, but nothing seems to work. I have good internet, so download isn't the problem, I have a 4-core processor, 16 gigs of ram, a 256 gig hard drive, and a high-end graphics card, so hardware isn't the problem either, so I have no idea what's going on. I'm using Ubuntu 14.04 on a 64-bit computer. If anyone can help, that would be great.