Use curl_file_create instead of @

[electblake]

I was receiving a curl error when running with latest php version (I believe 5.5.x)

I fixed the error in my fork via these 2 commits specifically:

electblake@1bf619c
electblake@0ad2a66

Let me know if you'd like me to branch out and send a pull request so fix can be merged into main repo.

Since I've stopped using cloudinary service, I may not be able to keep my fork updated.