Doesn't really affect the pages on the web, but it's easier to
preview them in the filesystem when linked to "../main.css" rather
than "/main.css".
The common portion of the <head> section is now in a separate
"include" file.
Added some indentation to masthead/topnav/sidenav so it looks nicer
in the merged source listing.
Added a SourceGen tutorial with lots of screen shots. Uses
"responsive web design" so it works well on mobile devices.
This version is using jQuery load() calls to pull in pieces, but
that causes a lot of blink when loading because the loads are
asynchronous and may not complete until after the initial page
render has finished.
Tutorial prev/next links not yet working.
