Make Challenge 2 in the novice shell lesson 5 consistent

This challenge used two different file names, neither of which was
consistent with part of the problem description. I chose the
longest.sh file name and made the challenge consistent for this
choice.
Typo fix in Challenge 4 of Novice Shell 5
Remove comparison of cp and mv from challenge in novice shell

Challenge 3 in /novice/shell/02 asks why mv and cp behave
differently in the case of providing multiple file names, but as
far as I can tell they behave exactly the same.
Merge pull request #411 from ethanwhite/shell-challenge-fixes

Shell challenge fixes