ROADMAP / TODO:

- [x] Search + Replace
- [x] Regex search + replace
- [ ] The undo system should actually work
- [x] Able to mark buffers as read-only
- [x] Built-in help text
- [x] Shorten paths in the homedir with ~
- [x] When the filename is longer than the message window, scoot left to
  keep it in view
