Stop on error to make it obvious when the setup fails

For example, if the user doesn't have write permission to ~/bin. This happened to me (I think I installed latex as root, maybe in a weird way - there are a bunch of latex scripts in my bin directory and bin was owned by root). I assume it printed out a permission denied message, but I didn't notice it, and at the end the setup.sh script printed "conscript installed to /home/donny/bin/cs".