Emerson professor David Gerzof Richard used Twitter to invite Patriots receiver Julian Edelman to talk to students in his social-media class, and No. 11 accepted. In previous years, Richard and his students tweeted at Pats tight end Rob Gronkowski and former receiver Chad Johnson, and both agreed to talk to the class. Edelman (inset), who has 119,000 followers on Twitter, said it can be useful in communicating with fans. “People around here love their sports, so it’s a huge tool for athletes,’’ he said.