Update articlesimportwordpress.class.php

[jacuve]

I had problems reading xml file, and the import makes nothing. because post_type was empty. Moved this lines to read the post_type from the namespace wp .

[JoshuaLuckers]

Thanks for your patience @jacuve. I know it has been a while but is this change needed because the WordPress XML file changed or did this never work? I want to figure out if it might break importing older WordPress XML files.