fixed URI.php to get cli arguments

Now, your code couldn't pass cli arguments to PHPUnit.

Because codeigniter blocks cli arguments to exec controller method from CLI.
http://ellislab.com/codeigniter/user-guide/general/cli.html

So, I fixed this when executing phpunit. 
Main point is L87. This is the only change point from original URI.php.

This PR would fix this.
https://github.com/fmalk/codeigniter-phpunit/issues/4#issuecomment-39589143


P.S. 
Your phpunit hack was so helpful to me. Thank you.