HBO Go (free) from Home Box Office, Inc. has been updated to version 2.1. The app, which lets HBO subscribers stream episodes on mobile devices, now features AirPlay multitasking capability. Now users can stream HBO video to AirPlay while continuing to use other apps on their iPad, iPhone, or iPod touch. Additionally, interactive features for the app’s Game of Thrones experience have been enhanced. Warner Bros. has brought Injustice: Gods Among…