Fixed localized providers directory structure to meet PSR-0 requirements

The namespaces of localized providers use underscores, which is in direct contradiction with PSR-0 guidelines.
The [PHP Framework Interop Group guidelines](http://www.php-fig.org/psr/psr-0/) states in its mandatory requirements:
> Each _ character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR. The _ character has no special meaning in the namespace.

As a result, the library cannot be used directly by autoloaders following PSR-0 standard strictly (like the one of Laravel for instance).

I've removed the underscores from directory names and updted the Factory::findProviderClassname() method.