examples: replace all app.Run(iris.Addr(...)) with app.Listen just for the shake of simplicity, both are doing the same exact thing as it's described on the http listening first example.

Former-commit-id: d20afb2e899aee658a8e0ed1693357798df93462

_examples/authentication/oauth2/main.go

@@ -400,7 +400,7 @@ func main() {
 	})
 
 	// http://localhost:3000
-	app.Run(iris.Addr("localhost:3000"))
+	app.Listen("localhost:3000")
 }
 
 type ProviderIndex struct {