The [README](https://github.com/aws/aws-encryption-sdk-java) says `(The AWS Encryption SDK for Java does not support the AWS SDK for Java 2.x.)` It also says to use: ``` <dependency> <groupId>com.amazonaws</groupId> <artifactId>aws-encryption-sdk-java</artifactId> <version>2.4.0</version> </dependency> ```` The [support policy](https://github.com/aws/aws-encryption-sdk-java/blob/master/SUPPORT_POLICY.rst) says `The AWS Encryption SDK follows the same major version lifecycle as the AWS SDK.` So I wonder what the meaning is of `2.4.0` and which AWS SDK I should use with it.