S3 headers

Our use case requires that we maintain all of our buckets in our production AWS account, and allow access to our testing AWS account via Cross Account Access: http://docs.aws.amazon.com/AmazonS3/latest/dev/example-bucket-policies.html

To allow the production account full access to objects uploaded by the testing account, we are setting the "x-amz-grant-full-control" header, and this pull request allows us to do so.

As we have an IAM policy to explicitly deny uploads from the testing account that don't set the "x-amz-grant-full-control header" to an expected value, I've also opted to catch the S3ResponseError.