Just in time for your Memorial Day road trip, it's goodbye Christian adult contemporary, hello R & B. Today iHeartMedia St. Louis announced that its short-lived Christian music station, "Up 103.7," has become "Majic 103.7," a.k.a. "Today's R&B and Throwbacks." The station officially debuted at 10:37 a.m. — meaning you can tune in right now for its first day, which includes 10,000 commercial-free songs in a row.…