def attr(name, str)
      case @xmlstack.last
      when :c
        @cell.send name, str if @cell.respond_to?(name)
      when :mergeCell
        @mergedcells << str if name == :ref
      end
    end
def attr(name, str)
      case @xmlstack.last
      when :c
        @cell.send name, str if @cell.respond_to?(name)
      when :mergeCell
        @mergedcells << str if name == :ref
      end
    end
Set cell value, style, etc. This will only happen if the cell has an
 actual value AND the parser's state is :c.
 If the state is :mergeCell AND the actual attribute name is :ref the
 attribute will be added to the merged cells array.
 The attribute name is tested against the Cell object: if the cell
 has a method named the same way, that method is called with the str parameter.
 @param [String] name of the attribute.
 @param [String] str Content of the attribute