I have created a pull request to update REP 3.
The change is very small and only explicitly mentions the required CMake version for Groovy.

CMake 2.8.3 has been selected since it is supported by all targeted Ubuntu versions (Oneiric and higher).
It provides common CMake functions like cmake_parse_arguments, which can than be used natively without the need to reimplement them.

If you are interested please take a look at the changeset: https://github.com/ros-infrastructure/rep/pull/3
Please comment directly on the pull request until the end of this week (Sunday, Oct. 7th).

- Dirk

PS: we are trying to use this kind of work flow (fork, modify, pull request, comment, reiterate, merge) more and more in the future...