title: Make QSpinBox.valueChanged() only respond to Mouse Wheel
body: <p>I have QSpinBox's Signal <code>valueChanged</code> connected to a QWidget's function like:</p>
  
  <pre><code>class MyWidget(QtGui.QWidget):
      def __init__(self, *args):
          QtGui.QWidget.__init__(self, *args)
          #just an example
          mySpinBox = QtGui.QSpinBox()
          mySpinBox.valueChanged.connect(self.foo)
  
     def foo(self):
         if value was changed by Mouse Wheel:
              #do this
         else:
              #do nothing 
  </code></pre>