A few vi/vim corrections

The package for gvim is vim-gnome, not gvim. When vim isn't installed, typing `vim` simply prompts you to install it (same as any other missing command) - it doesn't fire up vi, and finally cursor keys *usually* work in vi (at least under most linux distros) because vi is usually implemented via the vim-tiny package (i.e. it's just running a cut-down version of vim) but it's still useful to list the HJKL mappings as it's possible that key mappings can get mucked up by various terminal emulators