removing dead code

concept introduced in 59282ba9997aa41661507a555356821a366f9854 was removed in 28de46f3b45a3ef1c3ee710b05b82fc3dc253db5
Merge pull request #2002 from michaelglass/patch-2

removing dead code
Provide a custom user agent header to cURL request so that URL shorteners are able to track the amount of downloads
Clean up downloader test a bit