Doc: Add Elysium to Easier Editing (issue 6488101)

[graham]

Hmm.  IMO, Elysium should be listed under the "text editors" section,
while the top "recommended" section should not be alphabetized.

However, I'm open to a re-think of the page, wherein we drop the
"recommended"-ness, and/or group programs differently, and/or whatever
else might be good to change.  I think we need to have *some* form of
organization beyond pure alphabetical, though, to help users to
understand the choices.

http://codereview.appspot.com/6488101/