i18n guide: fix external link to rack locale

railties/guides/source/i18n.textile

@@ -278,7 +278,7 @@ def extract_locale_from_accept_language_header
 end
 </ruby>
 
-Of course, in a production environment you would need much more robust code, and could use a plugin such as Iain Hecker's "http_accept_language":http://github.com/iain/http_accept_language/tree/master or even Rack middleware such as Ryan Tomayko's "locale":http://github.com/rtomayko/rack-contrib/blob/master/lib/rack/locale.rb.
+Of course, in a production environment you would need much more robust code, and could use a plugin such as Iain Hecker's "http_accept_language":http://github.com/iain/http_accept_language/tree/master or even Rack middleware such as Ryan Tomayko's "locale":http://github.com/rack/rack-contrib/blob/master/lib/rack/contrib/locale.rb.
 
 h5. Using GeoIP (or Similar) Database