He set the fashion world on fire, and there's a good chance that you can't say his name: Demna Gvasalia (pronounced DEEM-Nah go-AH-Liyah). Learn it fast. As both the principle Vetements designer and the new artistic director of Balenciaga, the 34-year-old from Georgia (the country, not the State) has risen in just a few short seasons of relative unknown to the most talked about the tastemaker on both sides of the Atlantic. Vetements impact, in particular, has been nothing short of seismic-especially on the street. During every month sets, which just wrapped up in the French capital, you can't take a Fendi bag without hitting an editor, designer or blogger wearing Hooded Jackets now the signature brand. Hooked, too, are high-powered celebrity Kim Kardashian, Rita Ora and Selena Gomez. Rihanna, you're never far from a trend, even came out last month in a head-to-toe of the hell hot spring lineup of the label. Not bad for an indie company that is almost as old as the North...