Yesterday we showed you how someone had added a spoof image on a Metro rail car suggesting that “Rapture” is a behavior that’s banned on the transit system. Today, WMATA’s director of public relations, Lisa Farbstein, sent us the agency’s response to the mystery culprit. “We may be a big agency, but we have a sense of humor too!” Farbstein wrote in an email. Tragically, the sign above won’t be added to any rail…