A good friend of mine wanted a README file on this project. Thus, there is now a README file. :D
If you don't have Rust; get it from http://rustup.rs. After that, run cargo install mathy-editor, and you're done!
Use this like a normal text editor; the useful part happens when you hit either Control + Enter or Shift + Enter. Experiment with it; if you do something you don't like, you can always Control + Z to undo.
If you have feature requests, head over to the Issues page and let me know; this is primarily a personal project, but it's also a fun showcase of what egui can do with relatively little effort. I'd be happy to add your suggestions!