What a pleasure it is to be treated that way by a brand-extension musical, a form usually characterized by craftlessness and cynicism. Indeed, at its best, “Water for Elephants” has more in common with the circus arts than it does with by-the-books Broadway. Sure, it features an eventful story and compelling characters, and apt, rousing music by PigPen Theater Co., a seven-man indie folk collective. But in the director Jessica Stone’s stunning, emotional production, it leads with movement, eye candy and awe.