Open /dev/tty in non-blocking mode

Resolves gdamore#452.

tscreen.go

@@ -1668,14 +1668,23 @@ func (t *tScreen) mainLoop(stopQ chan struct{}) {
 }
 
 func (t *tScreen) inputLoop(stopQ chan struct{}) {
-
 	defer t.wg.Done()
+	var (
+		n   int
+		err error
+	)
 	for {
 		select {
 		case <-stopQ:
 			return
 		default:
 		}
+
+		err = t.in.SetReadDeadline(time.Now().Add(250 * time.Millisecond))
+		if err != nil {
+			panic(err)
+		}
+
 		chunk := make([]byte, 128)
 		n, e := t.tty.Read(chunk)
 		switch e {