title: capture Tag visualizer contact event
body: <p>I'm developing Microsoft Surface(pixelsense) App using TagVisualizer object
  I'm looking for a method to capture tagEnter, tagLeave event on other UI elements such as a button.
  For example in following XAML code I want to capture an event when TagVisualizer enters the boundary of "Button1".</p>
  
  <pre><code>  &lt;Grid&gt;
      &lt;s:TagVisualizer 
          Name="MaintagVisualizer" VisualizationAdded="MaintagVisualizer_VisualizationAdded" 
          VerticalAlignment="Stretch" 
          HorizontalAlignment="Stretch" 
          HorizontalContentAlignment="Center" 
          Height="Auto" Width="Auto"
          VerticalContentAlignment="Center" &gt;
  
          &lt;s:TagVisualizer.Definitions&gt;
              &lt;s:TagVisualizationDefinition LostTagTimeout="2000" MaxCount="1" Value="0x1" Source="TagVisualizationEllipse.xaml" /&gt;
          &lt;/s:TagVisualizer.Definitions&gt;
  
          &lt;s:SurfaceButton Name="Button1" HorizontalAlignment="Left" VerticalAlignment="Top" Content="test" Width="120" Height="40" Margin="20" &gt;&lt;/s:SurfaceButton&gt;
  
      &lt;/s:TagVisualizer&gt;
  &lt;/Grid&gt;
  </code></pre>