Minor fixes to image filepath and namespace

I was getting some errors that the class "PKPass" didn't exist, and that icon.png was not set when it was.

I fixed the class error by changing the instantiation of the class in example.php as new PKPass\PKPass();

Also, when the code is setting the filename as the index in the files array, it is defaulting to using the full path to the file as the filename when it's not set instead of using the basename. these commits fix that as well.