In Jason Reitman ’s “Saturday Night,” we meet the original Not Ready for Prime Time Players mere minutes before they revolutionize comedy — and television itself — with their live, late-night NBC variety show dreamed up by an inscrutable Canadian named Lorne Michaels. Buzzing with nervous energy, the film tick-tocks through the chaotic final 90 minutes before the first episode of “Saturday Night Live” (which at that point didn’t have the “Live” in its title) hits the air on October 11, 1975. We