In this example, a thread is run in the model as the button is
pressed. The thread changes the model busy status, and
increments 10 times the value of property counter. The
controller observes the model properties and updates the view
accordingly. The model uses the gtk idle function to notify the
controller, so the thread changing the model and the controller/view
are isolated, and the view got updated by the same thread running the
gtk main loop.

To run: 
$> python main.py 

... from within the directory where this file is located
