Investors should pay attention to this booming restaurant enterprise.Chipotle Mexican Grill (CMG -2.14%) has crushed the market. In the past five years, shares have quadrupled, a gain that might come as a surprise to investors believing this kind of return can only come from technology enterprises.As of this writing, though, this restaurant stock trades 12% off its all-time high from earlier this year. This dip might prompt investors to buy shares. But before doing so, here are three must-know facts about C ...