Each Friday, Roads & Kingdoms and Slate publish a new dispatch from around the globe. For more foreign correspondence mixed with food, war, travel, and photography, visit their online magazine or follow @roadskingdoms on Twitter. TSETSERLEG, Mongolia—As the crow flies, Gaaj, one of Mongolia’s 800,000 fully nomadic citizens, doesn’t live too far from Ulaanbaatar, the country’s capital and only metropolis....