Biggest Overstocktober Event in Company History SALT LAKE CITY, 2015-10-5 — /EPR Retail News/ — Overstock.com, Inc. (NASDAQ:OSTK) is celebrating the shopping website's 16th birthday with its largest annual Overstocktober event, being held Oct. 1 through Oct. 16. The online retailer has pumped up its traditional birthday sales event to mark the birthday milestone, with savings of 16…