By using a resumable digester and storing the state of upload digests between
subsequent upload chunks, finalizing an upload no longer requires reading back
all of the uploaded data to verify the client's expected digest.
Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
middleware concept.
This also breaks the dependency the storage package had on goamz
Signed-off-by: David Lawrence <david.lawrence@docker.com> (github: endophage)
