Loop support

The lack of "loop mode" is the first thing I noticed with this bundle.

I have overriden ```mageekguy\atoum\scripts\runner::loop()``` to kind of fix the ```passthru()``` call, calling back the Symfony command. 
As arguments/options handling of atoum and symfony commands is a bit different, I simply and roughly fed back all the original options and arguments to the command, handling only score file as in the original ```loop()``` function.

I guess this is a bit dirty, and I don't know everything I'm doing :dog: