Fix for issue #109 - After uploading a video the thumbnail is missing

[bluengreen]

Added resource_type to $cloudinary.url call to get correct url for video thumbnails

[orlando]

Hey @bluengreen can we add a small test for this please?

Also, what about squashing these commits?

Thanks!

[bluengreen]

Is there an existing test for that code?

[orlando]

I don't think we have a test for the thumbnail generation. I'll say that is fine add this to https://github.com/assembler/attachinary/blob/master/spec/features/notes_spec.rb.

Also if you can add a bit of context to this PR, I know that cloudinary defaults to resource_type: image, but why we are doing this instead of using resource_type: auto for example.