Resources ending with .html should have the .html stripped

[white-gecko]

#94 was not fully implemented:

Further if there are resources ending with .html the behavior should be as follows:

<http://ex.org/e.html>    -> /e.html
<http://ex.org/f>         -> /f.html

The following setup should throw an error for now.

<http://ex.org/g.html>    -> x
<http://ex.org/g>         -> x