Burrito-centric restaurant chain Chipotle Mexican Grill (CMG -0.79%) made its public market debut way back in 2006. But in June, it plans to do something it's never done before: split its stock.Management is proposing a massive 50-for-1 stock split, meaning investors will receive 49 additional shares for every share they currently own. It's not quite a done deal yet as the plan needs shareholder approval, but it's likely to go through.Stock splits are enjoying their time in the financial headlines. However, ...