Urdf shapes fix

Now you can draw other shapes.

Example, try:
roslaunch urdf_tutorial display.launch model:=urdf/05-visual.urdf
rosrun tf2_web_republisher tf2_web_republisher
roslaunch rosbridge_server rosbridge_websocket.launch

and open on browser: examples/urdf.html

![r2d2](https://f.cloud.github.com/assets/4551246/2172364/50b26828-9592-11e3-8e9f-1d330cee0e88.png)