The title of American Authors’ new hit, “The Best Day of My Life,” is becoming increasingly prophetic. Last week’s seven days, when the group made its Billboard Hot 100 debut at No. 93 with the song, certainly must’ve been up there for the Brooklyn-based quartet of Berklee College of Music classmates. This week, “Best Day” breaks into the top 10 on the Adult Top 40 chart (rising 14-10) and holds its bullet at No. 22 on the Triple A tally.