Update wxpython.py example for wxPython 4.0 (cztomczak#348).

Thanks to Andrew Leech for the patch.

Author: cztomczak

docs/Tutorial.md

@@ -7,8 +7,8 @@ a replacement for standard GUI toolkits such as wxWidgets,
 Qt or GTK. With this tutorial you will learn CEF Python
 basics. This tutorial will discuss the two basic examples:
 [hello_world.py](../examples/hello_world.py)
-and [tutorial.py](../examples/tutorial.py). There are more
-many more examples that you can find in the [Examples-README.md](../examples/Examples-README.md)
+and [tutorial.py](../examples/tutorial.py). There are many
+more examples that you can find in the [Examples-README.md](../examples/Examples-README.md)
 file, but these examples are out of scope for this tutorial.
 
 
@@ -33,8 +33,7 @@ You can install with pip. On Linux pip 8.1+ is required. Alternatively
 you can download packages for offline installation from [GitHub Releases](../../../releases).
 
 Run the commands below to install the cefpython3 package, clone
-the github repository, enter the examples/ directory and run the
-Hello World example:
+the repository and run the Hello World example:
 
 ```commandline
 pip install cefpython3==56.1

examples/wxpython.py

@@ -109,7 +109,7 @@ def create_menu(self):
 
     def embed_browser(self):
         window_info = cef.WindowInfo()
-        (width, height) = self.browser_panel.GetClientSizeTuple()
+        (width, height) = self.browser_panel.GetClientSize().Get()
         window_info.SetAsChild(self.browser_panel.GetHandle(),
                                [0, 0, width, height])
         self.browser = cef.CreateBrowserSync(window_info,
@@ -197,14 +197,15 @@ def create_timer(self):
         # http://wiki.wxwidgets.org/Making_a_render_loop
         # Another way would be to use EVT_IDLE in MainFrame.
         self.timer = wx.Timer(self, self.timer_id)
+        self.Bind(wx.EVT_TIMER, self.on_timer, self.timer)
         self.timer.Start(10)  # 10ms timer
-        wx.EVT_TIMER(self, self.timer_id, self.on_timer)
 
     def on_timer(self, _):
         cef.MessageLoopWork()
 
     def OnExit(self):
         self.timer.Stop()
+        return 0
 
 
 if __name__ == '__main__':