Reviewed by GREG KING Directors: Joel and Ethan Coen Stars: Oscar Isaac, Carey Mulligan, John Goodman, Justin Timberlake, Jeanine Serralles, Ethan Phillips, Robin Barrett. This bittersweet and blackly funny film follows a week in the life of a down and out folk singer struggling to make his mark in the early 60s when folk was slowly taking over from jazz in the Greenwich Village coffee houses frequented by the …