def td(name, options = {}, &block)
      column_class = options.delete(:using) || Column
      @columns << column_class.new(name, options, &block)
    end
def td(name, options = {}, &block)
      column_class = options.delete(:using) || Column
      @columns << column_class.new(name, options, &block)
    end
TODO: spec & doc for using option