Detect PSR-0 usage

[jenkoian]

Perhaps out of scope for this tool, but am interested in hearing your feedback.

Add a check for the now deprecated PSR-0 standard http://www.php-fig.org/psr/psr-0/

I guess you would need to check the composer.json which is why I'm not sure if in scope for this tool.

[ghost]

Since we do use the composer.lock if available, the check could be included for a composer.json
I think we anyway need to parse the composer.json in case the vendor directory has a non-default path