Version 3.18.0

• Aws\CognitoIdentityProvider - Added support for the Amazon Cognito
  Identity Provider service.
• Aws\ElasticBeanstalk - Added support for automatic platform version upgrades
  with managed updates.
• Aws\Firehose - Added support for delivery to AWS Elasticsearch Service.
• Aws\Kinesis - Added support for enhanced monitoring.
• Aws\S3 - Added support for S3 Accelerate.
• Aws\S3 - Fixed bug where stat cache was not being updated following writes.
• Aws\Signature - Fixed inefficiency in S3 presigner.