By Martin Baccardax Costco took in $984 million in new membership fee in its fiscal third quarter, helping the bulk retailer top Street forecasts for topline revenues. Costco Wholesale Corp. (COST) – Get Costco Wholesale Corporation Report posted third quarter earnings that were largely in-line with Wall Street forecasts, with modestly higher sales, as the bulk retailer used its cheaper members-only gasoline sales to bring in customers in a challenging retail environment. Costco said diluted earnings for the three months ending on May 8, the company’s fiscal third quarter, came in a $3.04 per …