Composer compatibility

As discussed in issue #19 there is a desire for this library to be loaded/included using composer.

This package has quite a nice method of loading classes/dependencies, but it would be much easier for developers if this was consistent with modern php standards and made use of autoloading.

As all classes have been renamed and namespaced this would need to form part of version 2 of getID3, and I think this would be a good time to look at adding unit testing, continuous integration, PSR compliance, and dropping support for unmaintained versions of php (safe_mode, magic_quotes, mysql_*, etc). I'm happy to help with all of this