Improve markdown guidelines wording

Amongst the changes here is that we do not need to have the hex or html
code (numbers) for open and close parentheses (in links) as there are
names. '(' is & followed by lpar; and the ')' is the same but 'rpar;'
instead. This makes it easier to remember and type and it generates the
same html as well (they are all valid). Now the markdown files are
consistent in this (in some cases hex was used and in others the html
code).

Although many markdown files were updated no html files needed to be
updated as it generates the same html. Even so I ran the appropriate
rules to do so just to verify this.

1991/README.md

@@ -77,7 +77,7 @@ us with your comments and suggestions today.
 
 For those who appreciate a bit of Internet history, this is how
 people used to contact the IOCCC in this given year, via [Unix to Unix CoPy
-(UUCP)](https://en.wikipedia.org/wiki/UUCP#Mail_routing):
+(UUCP)](https://en.wikipedia.org/wiki/UUCP#Mail_routing):
 
 >   ...!{sun,pacbell,uunet,pyramid}!hoptoad!judges<br>
 >   judges@toad.com