Bump version to v2.0.0.rc8
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.
Fix NameError for `412Error` on 412 without body

>> Aws::S3.new.head_object(if_unmodified_since: '2014-06-09 12:44:21 +0900', bucket: '...', key: '...')
NameError: wrong constant name 412Error
Merge pull request #65 from sorah/fix-412error

Fix NameError for `412Error` on 412 without body
Added support for S3 serversSide-encryption with customer-provided keys.
Added integration for customer-provided sse keys.
Added support to Aws::SNS for publishing with message attributes.
Added support to Aws::Redshift for cluster identifiers.
Bug fix for EC2 copy snapshot.
Resolved an issue with empty body errors from Aws::S3.

Now prefixing the error class name with "Http" to prevent
ruby from raising an error about invalid constant.

Fixes #66
Fixed a testing order bug.
Resolved an issue where the target IO was not rewound for streaming operations.

Given the following:

    s3 = Aws::S3.new
    s3.put_object(bucket:'name', key:'key', body:'hello')

The following code would always return an empty string,
until you called `#rewind`:

    resp = s3.get_object(bucket:'name', key:'key')
    resp.body.read
    #=> ''

    resp.body.rewind
    resp.body.read
    #=> 'hello'

This commit patches the http handler to rewind the http response
body IO object before returning. Now the following works:

    resp = s3.get_object(bucket:'name', key:'key')
    resp.body.read
    #=> 'hello'

Added an integration test to prevent regression.

Fixes #67
Now serializing empty lists for the query protocol.

Fixes #49