Add div id to target in the display so examples get displayed in the right tag (#955)

* Add target to display

* Remove output from examples

examples/matplotlib.html

@@ -15,7 +15,7 @@
         ]
       </py-config>
 
-      <py-script output="mpl">
+      <py-script>
 import matplotlib.pyplot as plt
 import matplotlib.tri as tri
 import numpy as np
@@ -48,7 +48,7 @@ tpc = ax1.tripcolor(triang, z, shading='flat')
 fig1.colorbar(tpc)
 ax1.set_title('tripcolor of Delaunay triangulation, flat shading')
 
-display(fig1)
+display(fig1, target="mpl")
       </py-script>
     </body>
 </html>