Get ready Kindle Fire fans, Amazon is throwing down the gaming gauntlet and taking on all comers. The content giant just announced GameCircle, a new tool available to developers publishing games on its customized Android platform. It allows the easy integration of an achievement system and leader boards that don't pull a user out of a game. Instead a simple pop up launches when you've been awarded a new trophy and closing it out lets you go right back to where you were (presumably cutting ropes, flinging birds or shooting zombies). Perhaps most exciting though, is the ability to sync
