Revert "Merge pull request #21 from AltGr/allow-url-mirrors"

This reverts commit 5a289c61c124922e045e813e768f78e276f53d04, reversing
changes made to 31c3dc9e8d6bb96bcbdc4f24ed37c12b5153f933.
Merge pull request #22 from AltGr/revert-mirrors-api-change

Revert "Merge pull request #21 from AltGr/allow-url-mirrors"