Add information about setting up PaperCut to README

[tsalo]

The instructions for setting up PaperCut (to print to the networked printers on campus) on your computer are no longer available at the link that was originally sent out. I know a couple of people in the lab had to set it up recently, so this is a good opportunity to codify the instructions.

[tsalo]

Thanks @Flanneryg3!