add Context.ResponseWriter.IsHijacked to report whether the underline conn is already hijacked and a lot of cleanup and minor ws stress test example improvements

Former-commit-id: 444d4f0718d5c6d7544834c5e44dafb872980238

_examples/mvc/hello-world/main.go

@@ -32,7 +32,7 @@ import (
 // for the main_test.go.
 func newApp() *iris.Application {
 	app := iris.New()
-	// Optionally, add two built'n handlers
+	// Optionally, add two builtin handlers
 	// that can recover from any http-relative panics
 	// and log the requests to the terminal.
 	app.Use(recover.New())

_examples/mvc/overview/web/controllers/hello_controller.go

@@ -23,7 +23,7 @@ var helloView = mvc.View{
 // Get will return a predefined view with bind data.
 //
 // `mvc.Result` is just an interface with a `Dispatch` function.
-// `mvc.Response` and `mvc.View` are the built'n result type dispatchers
+// `mvc.Response` and `mvc.View` are the builtin result type dispatchers
 // you can even create custom response dispatchers by
 // implementing the `github.com/kataras/iris/hero#Result` interface.
 func (c *HelloController) Get() mvc.Result {