Teased at this year’s Pebble Beach Concours d’Elegance in a menacing matte black with neon-orange accents, the BMW M4 GTS is officially coming to the United States as a street-legal road car. The German marque announced yesterday that only 700 of the special-edition M4s will be made, 300 of which will be allocated for the United States. The M4 GTS is 200 pounds lighter than the stock M4, thanks to aluminum and carbon fiber throughout, and it showcases two industry firsts for a production road car: a water-inje…