All teenagers have been warned: “don’t give into peer pressure.” We hear that peer pressure can do things like lead to drugs and binge drinking and unplanned pregnancies. Maybe peer pressure will make you drop out of school and join a gang.  But in Tina Rosenberg’s opinion, peer pressure isn’t all bad. The Pulitzer Prize-winner is the author of a new book called “Join the Club: How Peer Pressure Can Transform the World.” She argues that peer pressure is a very versatile tool.