The Mexican fast-casual chain is heading toward an unusual 50-to-1 stock split.Chipotle Mexican Grill (CMG 0.20%) is having a moment. The company's stock has been red-hot this year, gaining about 70% since last November. And now, investors are looking forward to its upcoming 50-to-1 stock split. When markets open on June 26, shareholders will own 50 times as many shares as they did at the close of trading on June 25, but the price of each one will be about one-fiftieth of what it was before. The stock split ...