Add an example of a "nice" shell script

[NicMcPhee]

Students often struggle with writing scripts that are (relatively) clean, well-organized, use names well, and have comments when appropriate. It might be useful to provide an example here of a script that has:

• Names for command line arguments
• Backslash line breaks to improve readability of long pipe chains
• Comments, especially on things like complex regular expressions that are otherwise very hard to read

Not all of this will apply to this lab, but it will apply to this and the next lab, so people might want to refer back to it, and there probably should be a mention in the write up for the next pre-lab to remind people that it's here.