For her third feature film “Nobody Walks” (opening October 19), thirty year-old writer/director Ry Russo-Young reached an enviable amount of career milestones. It was her first time working with a relatively mainstream cast (John Krasinski, Olivia Thirlby, Dylan McDermott and Justin Kirk, among others). It was her first screenwriting collaboration with Lena Dunham, creator of the hit HBO series “Girls,” who happens to be a