It might be ''Game Over'' for Flappy Bird on the iTunes store, but its still possible to install and play the game.
Download and install iFunBox to your computer
Connect iPhone to your computer
Open iFunBox and click the <<Install App>> button
Open the Flappy Bird .IPA file
Settings > Security > Enable Unknown sources
Open a web browser and download the Flappy Bird zip file
Open and install the file (.apk)