mark REP 140 final

The initial request for comments was posted to ros-users and the ROS buildsystem SIG (http://lists.ros.org/pipermail/ros-users/2013-July/053367.html).

After lengthy discussions and several updates a consensus was reached on the pull request with informal voting: https://github.com/ros-infrastructure/rep/pull/59

@tfoote @jwwood Please review.