This series is getting less predictable, and thus more satisfying, as it nears the end of its first season. (HBO already has renewed the show for a Season 2.) The characters, by now firmly established, are starting to react in ways that demonstrate growth, or change, or at least a reckless sort of aimlessness. And tonight, there’s a noteworthy guest star as well: Michael Imperioli of The Sopranos, playing a former writing professor of Lena Dunham’s Hannah.