Actually use storage-class in put-object

the DisplayName element in the list-bucket-result seems optional

I tested it with Amazon S3 and got a response with no DisplayName
element, which broker parsing the response

Support for S3 object tagging

Add the ability to set content type and content disposition to AUTHOR…

REGION-ENDPOINT should return the correct value for non-amazon providers

Include header x-amz-security-token in bucket-location request

use drakma:header-value

Exponential back off for 50x responses, and export accessors for responses.

Compute md5 sums not only for pathnames

Capitalize percent codes. This is to match Amazon convention as reported in issue #21.

Thanks to Nick Levine for the patch, lightly modified and documented by
me.

Fix X-Amz-Expires header (must be delta seconds)