Release v2.1.21 - 2015-09-15

Tag release v2.1.21

References:
#923

• Feature - Aws::EC2 - Added two new fields to expose data encryption key id,
  and state message.

• Feature - Aws::EC2 - Added support for the new "Diversified" allocation
  strategy.

• Feature - Aws::ElasticFileSystem - Added support for optional mount
  target ID to the DescribeMountTargets operation.

• Feature - Aws::Route53 - Added support for calculated health checks and
  latency health checks.

• Issue - Aws::S3 - Resolved an issue which could raise a signature error
  when making reqeusts against an object where the key is prefixed
  with the bucket name. This only affects classic S3 signatures, not requests
  using signature version 4.

  See related GitHub issue #923.