Changed the file extensions to .php

Changed the file extensions of the pages to .php from .html and update
the links within the pages.
Created a separate head.php file for the head section

Created a separate head.php file for the head section of the html and
included it in all the pages
Created a separate footer.php file for the footer

Created a separate footer.php file for the footer and included it in all
of the pages
Created a separate nav.php for the navigation

Created a separate nav.php for the navigation, with a function to get
the current location and update the active page accordingly.
Changed footer.php to get the current year

Changed footer.php to get the current year for the copyright message,
rather than using a static one.