FROM SAYING "BAH, HUMBUG!" What was a single cowboy to do during the holidays? After five lonely Christmases, Jonah Fargo had no stockings to hang on the mantel and no cheek to kiss under the mistletoe. All he could do was sulk-and scare off the Christmas carolers. TO SAYING "I DO!" But then, a miracle came to Montana in the sexy form of Harmony Davis. The angel-faced beauty spread her holiday spirit and Christmas cupids all over Jonah's ranch. He griped, he grumbled-until something utterly incredible happened.