By Tzvi Machlin Grayson Murray may not be a household name in the golf world. But he’s quickly becoming one in this final round of the U.S. Open for the meltdown he’s been having. After a birdie on his first hole, it seemed like Murray might be in for a big day and maybe even his highest finish ever at a major. But things quickly went south – as did Murray’s composure. On the seventh hole, Murray had a quadruple bogey and tossed his club like a tomahawk in the process. But the meltdown was complete on the tenth hole. Murray hit his ball into the rough and knew immediately that he would struggl…