Add sub_menu in r_tags

lib/parsers/parser_common.rb

@@ -106,4 +106,20 @@ module ParserCommon
     page_menu.swap(fragment)
   end
 
+  # sub_menus
+  def parse_sub_menus(body = nil, page = nil, id = nil)
+    body.css('sub_menu').each do |sub_menu|
+      res = ''
+      res << "<ul>"
+      page.children.each do |child|
+        res << "<li>"
+        res << "<a href='#{child.full_name}'>#{child.i18n_variable[I18n.locale]}</a>"
+        res << "</li>"
+      end
+      res << "</ul>"
+      fragment = Nokogiri::HTML::DocumentFragment.new(body, res)
+      sub_menu.swap(fragment)
+    end
+  end
+
 end