use new rospy publisher syntax to avoid hanging

[tfoote]

Take advantage of: ros/ros_comm#308

[tfoote]

Cherry picked into indigo: fd73a6f

[venabled]

Just as a heads up @tfoote , In order to publish high-rate transforms, or multiple transforms in a single callback I needed to increase the queue_size in the TransformBroadcaster class. Would recommend that you either increase queue size or allow it as a parameter to be passed into the class constructor.