[webteam] intro pages

[Peter Saint-Andre]

I just finished some edits to the "intro" pages:

http://stage.jabber.org/what-is-jabber

http://stage.jabber.org/what-can-i-do-with-jabber

I still haven't looked at how those pages work with the following:

http://stage.jabber.org/why-use-jabber

http://stage.jabber.org/quickstart

Feedback is welcome as always. I find that it's really hard to summarize
what Jabber is in just a few words...

Peter