def []=(key, value)
      if columns.key?(key)
        @array[columns.index(key)] = value
      else
        @array << value
        columns << key
      end
      hash[key] = value
    end
def []=(key, value)
      if columns.key?(key)
        @array[columns.index(key)] = value
      else
        @array << value
        columns << key
      end
      hash[key] = value
    end
Set cell value. Adds cell to end of Row and adds new Column if there is no Column for +key_