Project rename

To make it possible to import github.com/xyproto/permissions instead of the more cumbersome github.com/xyproto/permissions2/v2, this package and all further developent has been moved to:

https://github.com/xyproto/permissions

The permissions2 repository will continue to exist like it is right now for backward compatibility with existing packages that imports github.com/xyproto/permissions2/v2, though.