Update ps3joy/package.xml URLs with github user ros to ros-drivers
Merge pull request #57 from felix-kolbe/patch-1

Update ps3joy/package.xml URLs with github user ros to ros-drivers
Remove quit on failed root level check, part one of issue #53
Improve ps3joy_node with rospy.init_node and .is_shutdown

Replace unused self.shutdown with rospy.is_shutdown()

Call rospy.init_node with anonymous=False because the hardware cannot be accessed multiple times concurrently
Refine diagnostics message usage in ps3joy_node