For four days the world converged on the hamlet of Manchester, Tenn. (pop. 10,000). Or so it seemed. This unassuming town surges to the state’s fifth-largest city when Bonnaroo gets under way every June. Named best festival by Rolling Stone magazine, the seven-year-old event is a four-day, multi-stage camping festival on a 700-acre farm 60 miles south of Nashville. Among…