'Return a |_Column| object of *width*, newly added rightmost to the
table.'

def add_column(self, width):

    tblGrid = self._tbl.tblGrid
    gridCol = tblGrid.add_gridCol()
    gridCol.w = width
    for tr in self._tbl.tr_lst:
        tc = tr.add_tc()
        tc.width = width
    return _Column(gridCol, self)
