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.

2012/blakely/README.md

@@ -33,7 +33,7 @@ For more detailed information see [2012/blakely in bugs.html](../../bugs.html#20
 Several IOCCC themes ([RPN
 calculator](https://en.wikipedia.org/wiki/Reverse_Polish_notation), animated
 [GIF](https://en.wikipedia.org/wiki/GIF) generator, [ray
-tracing](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)) graphics) in one package!
+tracing](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)) graphics) in one package!
 Very impressive!
 
 The checkerboard pattern in the output can be broken. Could you figure out how?
@@ -47,7 +47,7 @@ Larger GIF files confuse some image viewers.
 
 This program renders a generic
 [RPN](https://en.wikipedia.org/wiki/Reverse_Polish_notation) expression in
-[ray-traced](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)) animated
+[ray-traced](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)) animated
 [GIF](https://en.wikipedia.org/wiki/GIF) form.  The expression in spatial
 variables `x` and `y` is specified on the command-line with the required
 resolution, and an animated GIF showing a fly-around of the resulting surface is