Fix TRAINVM-18

I've created a setup script to install all of the `pe-ruby` RPMs. Once the RPMs are installed the script creates a file called `.extendingrc` in `/root/`. If the script is ran again and the file still exists it will exit with a message.

The remove script will not run unless the `.extendingrc` file exists and it simply runs `rpm -e --nodeps pe-ruby*`.