Updating to newest version to use the leg_detector in people_tracker

This merges in the latest changes from the main repository which include the leg_detector. The detector does not give the best results (human has to be quite close to the robot to be detected), but it works at 180 degrees and compliments the upper_body_detector.

To compile you need the kalman_filter package from the ros repos which does not have a rosdep definition. Therefore it has to be installed manually: `sudo apt-get install ros-hydro-kalman-filter`