Use Groupon Payments for your business? You just got a little more choice -- the popular deal broker just updated its Android app to support credit card transactions. The update brings the fledgling payment service a little closer to Square, which has been available on Android since 2010. If the iOS rates hold, swiping plastic through Groupon Merchants will set retailers back a mere $0.15 per transaction, plus 1.8 percent of the charge for Visa, MasterCard and Discover, or three percent for American
