Channing Tatum is joining the cast of “Kingsman: The Golden Circle,” tweeting the news on Wednesday evening. I'm about to get all up in that Golden Circle. #Kingsman pic.twitter.com/LqCPJ6monO — Channing Tatum (@channingtatum) April 14, 2016 Sources also tell Variety that Elton John is in talks for a key role. Matthew Vaughn is returning to...