rosdep: fixed rubygems version for quantal and raring

Replaced `rubygems` entries in for rosdep key `ruby` by `rubygems1.9.1` for Ubuntu quantal and raring.

`rubygems` without a version depends on `ruby1.8`, which does not match the installed dev package (http://packages.ubuntu.com/search?keywords=rubygems).

I guess this could be the reason why [orogen builds currently fail](http://jenkins.ros.org/view/HbinQ32/job/ros-hydro-orogen_binarydeb_quantal_i386/26/console) on Jenkins (@smits).