It will take more than Olympic gold to come between Kenyan marathon runners, neighbours and best friends Mary Keitany and Edna Kiplagat. London marathon winner Keitany and world champion Kiplagat are favourites for the gold in London on Aug. 5. "For us we have known each other for so long, so we have no differences," Kiplagat tells Reuters while squeezed next to Keitany on a sofa by the fire on a chilly evening in Iten, a small town 2,400 metres above sea level in western Kenya's Rift Valley. "We have been friends, we have been running together. She is like…