Examples:keyboard_listener.py change `request_keyboard` to be compatible

with current master

examples/widgets/keyboardlistener.py

@@ -4,12 +4,13 @@ kivy.require('1.0.8')
 from kivy.core.window import Window
 from kivy.uix.widget import Widget
 
+
 class MyKeyboardListener(Widget):
 
     def __init__(self, **kwargs):
         super(MyKeyboardListener, self).__init__(**kwargs)
         self._keyboard = Window.request_keyboard(
-            self._keyboard_closed, self)
+            self._keyboard_closed, self, 'text')
         if self._keyboard.widget:
             # If it exists, this widget is a VKeyboard object which you can use
             # to change the keyboard layout.