Added the ability to rename existing pages.
[[!redirects Some Page Name]] redirects Wikilinks [[Some Page Name]] to
the current page (assuming "Some Page Name" does not exist).
Real pages trump redirects (though this may change, depending on
user feedback).
This works fine with the default Webrick. But, if you're running under Mongrel (say), you probably
want to customize this in config/environments/production.rb .
