When Blitzen Trapper’s last record, Wild Mountain Nation, burst on the scene in June 2007, it was a breath of fresh air just as the summer heat wave struck. The opening Neil Young guitar peals of the title track and the rollicking campfire singalong “Country Caravan” had the internet going crazy, but the record itself — for all its jumps in style and frenzied rhythms — was a slow-burner, rewarding the fans who stuck around…