If you’re a comic book fan, “Red Robin” is one of the superhero aliases used by Batman’s sidekick. But if you’re a hamburger fan, the name likely makes you think of Red Robin Gourmet Burgers and Brews and a bottomless basket of fries before the Boy Wonder. Despite some splashy successes, and some truly excellent boozy milkshakes, the once-mighty eatery has tumbled from the highest branch in recent years. So what happened?