Fixed depth cloud example
This fixes two problems with the depthcloud example
 - First the command to run the ros_web_video command was missing an underscore so the parameter to enable the web server was not set
 - Second the openni kinect driver only outputs uint16 depth images, while the depthcloud_encoder expects floats
   This adds a converter to generate float images
Merge pull request #83 from mitchellwills/develop

Merged and updated [the ROS WikiTutorial] (http://wiki.ros.org/ros3djs/Tutorials/Point%20Cloud%20Streaming%20from%20a%20Kinect) accordingly. Thanks!