Despite the deep, often dark places he goes for a character, Michael Fassbender often bounces back with the lightness of an Irish featherweight. When he’s not playing a menacing slave owner or a hunger-striking Bobby Sands, Fassbender is easygoing and playful — certainly not brooding. Lately, Fassbender’s job has been expanding. He not only stars in the Western “Slow West,” but it’s also the first feature from his production company, DMC Films. In the film, which opens Friday, Fassbender plays a hardened bounty hunter, chewing on the same cigarillos Clint Eastwood munched on, who takes in a young romantic traveler from Scotland pursuing his love. For Fassbender, a fan of both Westerns and Eastwood, “Slow West” is his chance to put his own stamp on the genre.