While all methods on tasks are called within the manager's lock,
dispatching to another queue obviously means the manager may not
be locked anymore.
I also moved calling progress download callbacks to the download
task so it's similar to progress image.
Hopefully these issues have been fixed, but it leads me to believe
a better architecture would be to make the tasks immutable by the
manager and have the tasks manage a lock on themselves. I'll need
to think about that more.
Mapping generic classes like PINImage, PINImageView and PINButton to the equivalent UIKit or AppKit classes. Throughout the framework use these mappings instead of the concrete UIKit / AppKit names. Furthermore we provide a category on NSImage that is adding methods that are not available on NSImage but on UIImage.
Previously the resultType was being returned
PINRemoteImageResultTypeDownload even when the download failed. Now, we
check to see if the image has been set and if it not then we return
PINRemoteImageResultTypeNone.
