* bugfix: strip uri prefix returned in uri from paged responses

I suspect this is actually a bug in the Sparkpost API provided by the vendor - but I would need to do further tests to verify this. Either way, I've coded a workaround which should hopefully work.

NOTE: this release is identical to the previous version uploaded. I accidentally entered the wrong version number (v2.2.1) into resource manager when uploading the previous version - but the download is actually v2.1.1. If you have already downloaded v2.1.1 you do not need to download this version.