user guide: preparing for multi-page generation

rb/assets/user_guide.html.erb

@@ -1,6 +1,6 @@
 <html>
   <head>
-    <title>RScons User Guide - Version <%= Rscons::VERSION %></title>
+    <title>RScons User Guide<%= subpage_title %> - Version <%= Rscons::VERSION %></title>
     <style>
       body {
         background-color: #CCC;