Support listing more than 1000 items in a bucket

Amazon only returns 1000 items at a time on a request for ListObject in a bucket, basically supporting pagination of responses.

The changes just keep track of where you are in the list (it's lexicographic order) and gets the entire contents of the bucket.  You could also do a check for a truncated on the ListObject ('<IsTruncated>true</IsTruncated>'), but that was a bit lower level.

The added test case works for me, but I'm having some problems with access to your bucket so YMMV.