Preserve the order in which meta-tags are specified.

    # Instanciate all loaded MetaTag implementations

    def load_meta_tags

      # instanciate builtin meta tags

      builtins = MetaTag.descendants

      builtins.each do |cls|

      # instantiate builtin meta tags

      @meta_tag_classes = MetaTag.descendants

      @meta_tag_classes.each do |cls|

        @meta_tags << cls.new

      end

      # Load user-defined meta-tags

      @meta_tag_paths.each do |path|

        if File.directory?(path)

          Dir[path+"/**/*.rb"].each {|file| require(file) }

          Dir[path+"/**/*.rb"].each do |file|

            require(file)

            init_remaining_meta_tags

          end

        else

          require(path)

          init_remaining_meta_tags

        end

      end

    end

      # Instanciate these meta tags.  When builtin implementation for

      # @tag already exists, replace it with user-defined one.

    # Instantiates meta tag classes that haven't been instantiated

    # already. This is called after each meta-tags file is loaded so

    # that the list of meta-tags will be in order specified from

    # command line.

    def init_remaining_meta_tags

      MetaTag.descendants.each do |cls|

        if !builtins.include?(cls)

        if !@meta_tag_classes.include?(cls)

          @meta_tag_classes << cls

          newtag = cls.new

          @meta_tags = @meta_tags.find_all {|t| t.name != newtag.name }

          @meta_tags << newtag