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/tutorial/caddy/server2/main.go

@@ -21,7 +21,7 @@ func main() {
 	// PUT http://localhost:9092/user/42
 	// DELETE http://localhost:9092/user/42
 	// GET http://localhost:9092/user/followers/42
-	app.Run(iris.Addr(":9092"))
+	app.Listen(":9092")
 }
 
 // UserController is our user example controller.