Instagram Gets First Major Update After Facebook AcquisitionInstagram on the iPhone just got its first major overhaul since Facebook bought the app for more than $1 billion, and it's a fairly big one. Version 2.5 of the photo-sharing app doesn't exactly change it out of all recognition, but it does add a whole new tab -- "Explore", shown above -- to replace the "Popular" section that showed photos with the most likes. You can still see those top-ranking sn
