Black Knights and Midshipmen can reconnect with old battle buddies and shipmates –- or talk smack to the OpFor —  no matter where they are during this weekend’s annual Army-Navy game thanks to a new social media app designed exclusively for sports fans. Dubbed PlayUp, which launched in October for iOS devices, the app provides public and private chat rooms around virtually every sporting event imaginable. But developers are partnering with Military Traveler — another new app created by a Marine Corps Harrier pilot who bills his base guidebook as “Yelp for iPhones”  — to do something special for one of…