Added a customFields options to qq.UploadHandlerForm.

Hi,

previously Django compatibility was covered in #268 and #150.

Yet in those cases, file uploads with ie8 and ie9 are not possible, because the csrf token can not be added to the request header, yet it must be passed as a form field.

This pull request makes this possible.

Let me know if there's anything that needs to be altered before you would consider pulling this in. 

Regards,

Marko Tibold