README: Initial translation & cleaning from wiki
README: Initial translation & cleaning from wiki

I took @dolan-peter's [HTML version](http://personal.morris.umn.edu/~dolan118/cs3403/labs/lab0.html, which converted from the earlier U of MN wiki version), and used `pandoc` to convert it to markdown. I then did an editing pass on everything but the three exercises themselves.
UMM-CSci-Systems/Command-line-introduction