Added compatibility with PHP 5.4+ built-in webserver

Phabricator requires mod_rewrite rule to emulate "routing"
interface between web server and PHP aplication. Since PHP 5.4 where
is built-in web server that can be invoked with
"PHP -S 127.0.0.1:8000", but since it's very simple it don't have
mod_rewrite functionality. But it have routing functionality if .php
file is given via command-line - so this simple fix allows to
use PHP 5.4+ built-in web server to start Phabricator. Useful for
hacking, developing and testing. Use like this:

"php -S 127.0.0.1:8000 ~/Documents/phabricator/webroot/ ~/Documents/phabricator/webroot/index.php"