* Create `docs/tutor.txt`
* Create `EXITING HELIX` and `DELETION` sections
* Create Insert mode, saving, and recap sections
* Create `MOTIONS AND SELECTIONS` section
* Add additional notes to `SAVING A FILE` section
* Remove extra blank lines in `SAVING A FILE` section
* Move `tutor.txt` to `runtime/`
* Add WIP message to end of tutorial
