Routing guide: improve documentation for the scope method, demonstrating use of named parameters

railties/guides/source/routing.textile

@@ -200,6 +200,16 @@ or, for a single case
 resources :posts, :path => "/admin/posts"
 </ruby>
 
+You can even set named parameters for the paths:
+
+<ruby>
+scope ":username" do
+  resources :posts
+end
+</ruby>
+
+This will provide you with URLs such as +/bob/posts/1+ and will allow you to reference the +username+ part of the path as +params[:username]+ in controllers, helpers and views.
+
 In each of these cases, the named routes remain the same as if you did not use +scope+. In the last case, the following paths map to +PostsController+:
 
 |_.HTTP Verb |_.Path               |_.action |_.named helper      |