These instructions have been supplanted by an automated, scripted installer, which lives here:
https://github.com/mikepurvis/ros-install-osx
Please try it out, and file bugs as required. Feel free to browse past versions of this gist as a historical curiosity, but I won't be monitoring or supporting it any more.
@Juxi The command line interface for catkin_tools changed slightly. I've updated the gist accordingly.
I've also switched this to be a desktop_full install, which seems to work well for me.