[Indigo] add explicit keyword argument queue_size for publisher

I see the following SyntaxWarning when using the InteractiveMarkerServer with Python:

```
/opt/ros/indigo/lib/python2.7/dist-packages/interactive_markers/interactive_marker_server.py:97: SyntaxWarning: The publisher should be created with an explicit keyword argument 'queue_size'. Please see http://wiki.ros.org/rospy/Overview/Publishers%20and%20Subscribers for more information.
  self.init_pub = rospy.Publisher(topic_ns+"/update_full", InteractiveMarkerInit, latch=True)
/opt/ros/indigo/lib/python2.7/dist-packages/interactive_markers/interactive_marker_server.py:98: SyntaxWarning: The publisher should be created with an explicit keyword argument 'queue_size'. Please see http://wiki.ros.org/rospy/Overview/Publishers%20and%20Subscribers for more information.
  self.update_pub = rospy.Publisher(topic_ns+"/update", InteractiveMarkerUpdate)
```

I'm not sure whether this should be fixed and if yes whether the ```queue_sizes``` I chose are appropriate...so this is open for discussion!
(I chose ```queue_size=30``` for update as the markers is re-initialized when I set it to only ```queue_size=1```. 30 is the default frame_rate in RVIZ.)