Additional fixes to the html.sed script

It now translates the characters '|' (pipe), '=' (equals) and '%'
(percent).

Checks were added in md2html.sh in the -s token=value so that token
cannot contain an = (equal), | (pipe) or a % (percent) and the value
cannot contain a | (pipe).

The reason that we cannot disallow a ';' or '&' is because the html
entities use those characters so if the sed script were to translate the
problematic characters it would cause a problem in the script.

Ran make www which updated 1988/robison/index.html and
1990/theorem/index.html.

1986/bright/README.md was fixed with the number of blank lines between
sections.

1986/bright/README.md

@@ -29,7 +29,6 @@ program.  This gives you a small example of what it is like to
 maintain the Bourne shell! :-}
 
 
-
 ## Author's remarks:
 
 No remarks were provided by the author.