Use a hash tag.
May not be exactly what you want but it solves the problem of removing the extension.
Say you have a html page saved as about.html
and you don't want that pesky extension you could use a hash tag and redirect to the correct page.
switch(window.location.hash.substring(1)){
case 'about':
window.location = 'about.html';
break;
}
Routing to yoursite.com#about
will take you to yoursite.com/about.html
. I used this to make my links cleaner.