So, you're obsessed with Flappy Bird, huh? Bummed that the developer, Dong Nguyen, removed it from the App Store? Well, if you ever downloaded it before, you're in luck! Here's how to get it back onto your iPhone or other iDevice (or even a friend's!): First, open up the App Store on your device. Tap on the "updates" tab in the lower right-hand corner. Next, tap "Purchased" near the top. Then, search…