Use string instead of boolean (#561)

lib/generators/annotate/templates/auto_annotate_models.rake

@@ -46,7 +46,7 @@ if Rails.env.development?
       'trace'                     => 'false',
       'wrapper_open'              => nil,
       'wrapper_close'             => nil,
-      'with_comment'              => true
+      'with_comment'              => 'true'
     )
   end