def add_cell(value = '', options = {})
      c = Cell.new(self, value, options)
      self << c
      worksheet.send(:update_column_info, self, [])
      c
    end
def add_cell(value = '', options = {})
      c = Cell.new(self, value, options)
      self << c
      worksheet.send(:update_column_info, self, [])
      c
    end
Adds a single cell to the row based on the data provided and updates the worksheet's autofit data.
 @return [Cell]