The fast-casual chain's split will have one of the highest multiples ever.Investors love a good stock split. Those events don't do anything more than split the same-sized pie into smaller pieces, but they only occur after a company's share price has soared, which generally indicates that the business is doing quite well. Even better, when management decides to split a company's stock, it implies that it thinks there's more growth coming.Chipotle Mexican Grill (CMG -1.33%) wowed Wall Street back in March wit ...