def each skip=dimensions[0], &block
      skip.upto(dimensions[1] - 1) do |idx|
        block.call row(idx)
      end
    end
def each skip=dimensions[0], &block
      skip.upto(dimensions[1] - 1) do |idx|
        block.call row(idx)
      end
    end
If no argument is given, #each iterates over all used Rows (from the first
 used Row until but omitting the first unused Row, see also #dimensions).

 If the argument skip is given, #each iterates from that row until but
 omitting the first unused Row, effectively skipping the first _skip_ Rows
 from the top of the Worksheet.