Victoria Beckham has long been the arbiter of trends that are about to pop. She was an early adopter of single-sole pumps over platforms, proved that bell bottoms are just as flattering as skinnies, and—oh hey—now she's hailing the return of the slip dress. While wearing a Louis Vuitton chantilly-lace trimmed version fall 2013 collection, the fabulous VB proves that a slip dress doesn't have to look like bedroom attire. As a matter of fact, you can even wear it to unexpected places, like a…