boxturtle deprecated for utexas-art-ros-pkg

[Jack O'Quin]

Since ROS cturtle is out and working fine, the boxturtle release is
now deprecated for utexas-art-ros-pkg.

Everyone should install ros-cturtle-base, using the standard ROS
download instructions:

http://www.ros.org/wiki/cturtle/Installation/Ubuntu

There is still a tags/boxturtle version that works with the previous
ROS release, but I have no desire to keep it up to date with recent
developments.