Fixing typo in guide, updating ActionMailer description and making the contributors list alphabetical

Fixed unescaped '<' and '>' chars on getting_started section that were causing w3c validation errors (plusplus textile extension was letting them go untextilized)

s/guides.rails.info/edgeguides.rubyonrails.org/ in a few places, and makes some links relative to work in either site

 * Changed to Rails 3.0.0-beta rails command from script/*
 * Changed contrived before_filter to be an authentication feature
 * Refactored code into partials, showed three different types of partial usage
 * Showed how helpers work and fit in

Signed-off-by: NCarl Lerche <carllerche@mac.com>

Also created http://github.com/mikel/getting-started-code which is
a copy of all the code in this guide.