Updated the rewrite rule to point to 16.04

as the default user manual to show

maharadocs-1.7/debian/maharadocs.postinst

@@ -115,7 +115,7 @@ cat > /etc/apache2/sites-available/mahara-manual-sphinx.conf << EOF
         RewriteEngine on
         RewriteRule ^(.*)/1.4_STABLE/(.*)$ $1/1.4/$2
         RewriteRule ^(.*)/1.5_STABLE/(.*)$ $1/1.5/$2
-        RewriteRule   ^/$  /en/15.10/  [R]
+        RewriteRule   ^/$  /en/16.04/  [R]
     </IfModule>
 
 </VirtualHost>