Added support for transitioning versioned S3 objects to Glacier.
Added a missing :step to the handler list validation message.
Updates for the S3Md5 plugin.

Updates include:

* Disabled checksums on empty body.
* Now using OpenSSL::Digest::MD5 instead of Digest::MD5.
* Expanded test coverage.
* Clarified configuration option.
Expanded the query param seralization to include the trailing '=' when the value is nil.
Added basic support for presigned v4 urls.
Added support to Aws::EC2 copying encrypted snapshots.

Added support for the 2014-05-01 API version.  The SDK
will automatically compute the additional request params,
`:destination_region` and `:presigned_url` on your behalf.
Removed some development cruft.
Updates AWS APIs.