Mobile payments pioneer Venmo was the brainchild of two University of Pennsylvania graduates who were freshman roommates in 2001: Andrew Kortina and Iqram Magdon-Ismail. The peer-to-peer startup was sold for million to Braintree in 2012, which was acquired by PayPal a year later. With Venmo, users receive and send payments using mobile devices and transactions are part of a social network. N ow the mobile payments space is heating up. Facebook’s Messenger offers payments, a consortium of banks launched Zelle, there’s Google Pay, and others. Venmo COO Michael Vaughan recently joined the Knowledge at Wharton show on SiriusXM channel 111 , on location at the Wharton Global Forum in New York , to talk about why he believes his company will stay on top.   An edited transcript of the conversation follows. Knowledge at Wharton: What’s been most interesting to you about the development of mobile payments?…