A billionaire investor with an eye for value bought a piece of this business.Shares of shoe and athletic apparel company Nike (NKE -0.25%) gained 11.3% during August, according to data provided by S&P Global Market Intelligence. For most of the month, the stock bounced up and down with the S&P 500. But it created some separation when news broke that Pershing Square had purchased a stake in the business.Pershing Square is the hedge fund for billionaire Bill Ackman -- a value-minded investor with plenty of na ...