VENTUREBEAT — Social app platform maker Sometrics is announcing today that ts virtual currency can be exchanged into Facebook’s own new virtual currency, Facebook Credits. The deal is a coup for the startup because it means that the rewards that its customers can earn on its Game Coins web site will be more liquid, allowing users to earn Facebook Credits (which can’t be spent in scores of Facebook apps) through acts such as browsing the web, shopping online, completing game missions, or writing game reviews...