Amy Schumer visited Jon Stewart on his final week hosting The Daily Show to plug her new movie Trainwreck — and also mention, uncomfortably, a morning news conference at which she’d plugged new legislation that would attempt to keep mentally unstable people from purchasing guns. "This horrible thing. This crazy shooting that happened, must have rocked you to your core," Stewart said of the two women shot to death while watching Schumer’s movie on July 23 by a man with a…