ROBBIO, Italy (Reuters) - Wine conjures up the image of cultured drinkers sipping their way delicately through a full-bodied vintage. But for two history buffs with a passion for the tipple, northern Italy has the barbarians to thank for its long wine-making tradition. Luca Sormani, from Como, and Fulvio Pescarolo, from the tiny town of Robbio near Milan, have traced the region's wine culture all the way back to its Celtic roots and have started making it according to ancient methods. Celtic tribes from farther north -- known to the Romans as "Barbari" -- conquered northern parts of Italy about...