Nothing really happens in Joe Swanberg’s new film “Hannah Takes the Stairs.” A small circle of post-collegiate Chicagoans negotiate the ambiguities of romantic engagement, talk a lot in close-ups as intimate as a pair of skintight Levi’s, and bathe frequently — with an unfussy and not particularly erotic regard for full frontal nudity. If, as “Seinfeld” creator Larry David once quipped, the TV series was supposed to be a “comedy about nothing,” it might be just as easy to dismiss “Hannah Takes the Stairs” as a solipsistic wallow in the MySpace angst of 20-something hipsters.