Rewrite "Versions" section

This rewrite explains how to use the Versions feature from the user's point of view. I took out the overly apologetic verbiage about accepting patches (I think being open to patches goes without saying).

P.S. Is hard-wrapping okay? I'm editing TTW on GitHub over here ...
Merge pull request #584 from whit537/patch-8

Rewrite "Versions" section