With healthy doses of exuberance and plenty of raucous, good-time rock ‘n’ roll, "Beatles ’64" takes music lovers on a captivating guided tour of the group’s maiden American voyage. John Lennon in "Beatles '64" To the filmmakers’ great credit, "Beatles ’64" always has one eye tightly focused on the future. Drawing its coda from 1975 interview footage, "Beatles ’64" leaves …