Juventas New Music Ensemble & OperaHub present Tramps, Emails & Hemlock Seully Hall, Boston Conservatory, 8 The Fenway March 18, 19, and 22 at 8 p.m., $6-$24 (20% discount if purchased through the Juventas web site) J. Jacob Krause was demanding something unusual of some singers leaning over some unusual props: more salivation directed at the laptops, please. Bostonist had slipped into Seully Hall in the midst of a dress rehearsal, where OperaHub and Juventas......