Rewrite all requests to the public folder.

This means that users can choose between:

 * Drop in install. http://localhost/php-mvc **just works**
 * Drop in install. http://localhost/ **just works** if in the document
 * root
 * Create a vhost pointing at the public folder

This removes the rewrite base which is unnecessary in most installs. and
prevents the possibility of putting the code in a different place or
even renaming the folder

fixes #79