Fix copying of files > 5GB via aws-fog.

[slonopotamus]

This change utilizes multipart-upload logic from Fog::AWS::Storage::File#copy that was added in
fog/fog-aws@e3a9a35

[jwstric2]

This would be a great addition, we were just pondering if the support for multipart uploads (were fixing to test 5 gig+ uploads) was there in carrierwave/fog integration

[mshibuya]

I would say that there's a design fault in fog-aws (similar methods Storage#copy_object and File#copy exist, but they behave slightly differently!), but working around this in our side sounds reasonable. I understand the pain of not being able to upload files more than 5GB size. It is common for the video files to exceed 5GB.

Thanks for the PR.

[slonopotamus]

As I understand it, Storage#copy_object (or maybe even all Storage#xxx methods) are kind of low-level API that directly maps to S3 calls. On the other side, File#xxx are higher-level functions that encapsulate underlying API calls in nontrivial ways.

[rsalehi2013]

@mshibuya any chance we can get a new release that includes this patch? thank you