When Mehan Jayasuriya (and a few others of us from the music staff) saw Passion Pit at the Black Cat last week, he got to see a scenario when a new band can’t quite rise to the level of its own hype. The Pains of Being Pure At Heart were up against similar, if slightly less daunting odds. Much like Passion Pit, they have only been together for about two years and only have a…