Robert Citrone, who runs the Tiger Cub firm Discovery Capital Management, has been determined to take advantage of the slide in oil prices. He hasn’t let holidays get in the way. On Thanksgiving Day, while many Americans were racing from their family feasts to the malls and stores, spending billions of dollars on TVs, toys and other items, Citrone and his team spent at least part of the day in their South Norwalk, Connecticut, office awaiting a decision from OPEC on whether the once-powerful cartel would cut...