Hamilton takes third F1 title after U.S. thriller

By Alan Baldwin AUSTIN, Texas (Reuters) - Lewis Hamilton joined the elite group of triple Formula One world champions on Sunday after winning a thrilling U.S. Grand Prix that kept the crowd on tenterhooks right to the very end. "That's the greatest moment of my life," he gasped over the team radio, choking back the tears, after crossing the line 2.8 seconds ahead of German team mate Nico Rosberg who had led before a late mistake. The first British driver to win back-to-back titles, Hamilton real