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.

2015/schweikhardt/README.md

@@ -185,7 +185,7 @@ which reports the limit in bytes, here 256KB. This allows to test
 whether a [Googol](https://en.wikipedia.org/wiki/Googol), which is
 10<sup>100</sup>, satisfies the conjecture. But what is a googol in hex?
 Fear not,
-[bc&#x28;&#x29;](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html)
+[bc&lpar;&rpar;](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html)
 to the rescue:
 
 ``` <!---sh-->
@@ -819,7 +819,7 @@ explore yet untested numbers for the rest of your life.
 
 The number of hex digits in the start number is limited by `ARG_MAX`,
 probably minus some overhead for the environment variables (use
-[env&#x28;&#x29;](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/env.html)
+[env&lpar;&rpar;](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/env.html)
 to trim your environment). In bits this leaves you with `2 to the power of (4 *
 ARG_MAX)`.