I skipped the season finale of Lost the other night in favor of another supernatural tale of attractive people haunted by their pasts who just want to get off the damn island. The Folger’s latest staging of The Tempest is a light, spritely, fleet-footed thing of a play, apropos for a show about forgiveness and renewal and the casting off of old follies. Like the shipwreck that opens Act I, it’s forceful and bewildering and…