By Nick Mulvenney ROSA KHUTOR, Russia Wed Feb 12, 2014 3:36pm EST (Reuters) – American cowgirl Kaitlyn Farrington stunned three former champions to win gold in the women’s snowboarding halfpipe by the narrowest of margins at the Sochi Olympics on Wednesday. The 24-year-old nailed her second run under the Extreme Park lights for a score of 91.75 to beat Australian defending champion Torah Bright by 0.25 of a point. Farrington, who needed to run in […]