1.2.0 to 2.1.3 backport missing

Hi, some minor changes introduced in the 1.2.0 version haven't been backported to the 2.1.3 version. The ones I've found are:

1. 2.1.3 [com.amazon.sqs.javamessaging.message.SQSMessage::setJMSDeliveryTime](https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/f9bde2d629adda51f7fdd2af958af0dbe11a693c/src/main/java/com/amazon/sqs/javamessaging/message/SQSMessage.java#L426) and ::getJMSDeliveryTime have a `FIXME` comment, while in the v1 a field [was added](https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/1aa7babcd36c38ef0a017f6b7a686cd67eb6437e/src/main/java/com/amazon/sqs/javamessaging/message/SQSMessage.java#L413)
2. 2.1.3 [com.amazon.sqs.javamessaging.SQSConnectionMetaData](https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/f9bde2d629adda51f7fdd2af958af0dbe11a693c/src/main/java/com/amazon/sqs/javamessaging/SQSConnectionMetaData.java#L39) defines JMS version as `1.1`, but depends on [jms-api 3.1.0](https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/f9bde2d629adda51f7fdd2af958af0dbe11a693c/pom.xml#L62). v1 metadata [was updated](https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/1aa7babcd36c38ef0a017f6b7a686cd67eb6437e/src/main/java/com/amazon/sqs/javamessaging/SQSConnectionMetaData.java#L40) to `3.1`.

There are also quite a few improvements to the comments, and minor code adjustments. But nothing noteworthy.

Come to think of it, it's not a backport, is it? Still, those changes should probably be forwarded to 2.x.x.