Revert "Accept either lower or upper cased method for sign"
Revert "Accept either lower or upper cased method for sign"

Develop promotes to master

This reverts commit e5c8c787e4138ff5e935384ce41802c54cd14478.

pivotal-golang/s3cli,pivotal-golang/s3cli,pivotal-golang/s3cli,pivotal-golang/s3cli