An S3 Bucket owner may wish to select a different underlying storage class
for an object. This commit adds an optional "storage_class" attribute to the
aws_s3_bucket_object resource so that the owner of the S3 bucket can specify
an appropriate storage class to use when creating an object.
Signed-off-by: Krzysztof Wilczynski <krzysztof.wilczynski@linux.com>