add style sheet

doc/coding_notes.html

 <!--#set var="banner" value="Coding Notes"-->
-<!--#include virtual="/perl/header"-->
+<!--#set var="stylesheet" value="css/zmap-default.css" -->
 <!--#set var="author" value="edgrif@sanger.ac.uk" -->
 
+<!--#include virtual="/perl/header"-->
+
+
   <p>This is simply a collection of notes about coding stuff to maintain consistency.</p>
 
   <P>A good way to maintain consistency is have the editor do the indenting/commenting