Add editor selection section.

I use vim as my VISUAL and EDITOR env variables because most tools that invoke those commands require an editor that works within a shell. For coding, I use Sublime Text though, so I had to do some code diving to figure out that I could specify an editor just for Qwandry (nice feature, btw).

I'm not sure why so man lines show edited below. I used GitHub's inline editor since this was such a simple change. I can fork and resubmit if you'd prefer to have a cleaner commit.