Demo tracking of a yellow ball.

visionDemo.cpp (and the other C++ files) can be compiled into a visionDemo
application which will track a yellow object and continually output which
direction the user should move to center it in the camera's field of view.
It should be cross-platform, but does rely on the iSight's 640x480 image, as
well as the iSight not needing undistortion.

sayFilter.py is a Mac OS X specific script which uses the command "say" that
is built in to OS X to provide user feedback.  It uses threading to ensure it
always speaks the latest command.

On a Mac the commands can be run from the command line as:
    visionDemo | sayFilter.py

---Jonathan Beall <jbeall@cs.hmc.edu>
   March 8, 2007
