Merge pull request #141 from hayesgm/master

Add support for Message Attributes
Add DelaySeconds to the Message struct.
Use Message.DelaySeconds in SendMessageBatch to set individual message delay in the batch.
Merge pull request #142 from zoips/message-delay

Enable individual message delay for SendMessageBatch
Explicitly close the response body, otherwise if ignored it causes a file i/o leak
Merge pull request #143 from hailocab/ioleak

Fix File I/O Leak
Use AWS Signature v4 in SQS. Among other things this enables support for 256 KiB payloads.
Update to 2012-11-05 protocol version
Check for response error before checking message attribute md5
Merge branch 'version-update'

Conflicts:
	sqs/sqs.go