Ax Extension Fix

Hi, I'm currently working on Implementing an OpenId Server and we needed AX functionality. I've been struggling with the Janrain lib and saw your post from a while back about the AX Extension.

I've added a registerRequest function to the Fetch_Response object that stores the request so when getExtensionArgs is called it'll used the stored one if it exists. Possibly not the cleanest fix but it seems to do the job.