It's time to sell short gold bullion and the miner ETFs because the yellow metal is in a leaking bubble that could lose more than half its value. So says Yoni Jacobs, executive director and chief investment strategist at New York City-based Chart Prophet and author of "Gold Bubble: Profiting From Gold's Impending Collapse," published by Wiley in April. IBD: What leads you to believe gold is in a bubble? Jacobs: In addition to the parabolic price