It's hard to find a more reliable market-beating stock than Costco Wholesale (COST -1.82%). It hasn't delivered the wildest gains, but it has climbed up steadily and without fanfare in an almost linear progression, missing the ups and downs of a typical stock trajectory.Even after rising 42% this year and hitting highs that make its valuation look enormous, it's not showing any signs of slowing down. Here's why, and why Costco stock deserves a place in your portfolio.Costco just raised its membership feeThe ...