By Alyson Kruger New kids Ari Melber, seen here with co-hosts Abby Huntsman and Touré Neblett, is part of a new wave of young cable-news hosts who come from backgrounds other than news. Melber is a lawyer, Huntsman worked on political campaigns, and Neblett was a music writer. (Charles Ommanney / MSNBC) On a Wednesday afternoon in...