Use only the S3 and EC2 parts of the AWS Java SDK

Note that jackson is not marked as optional in the SDK POM, and the SDK uses Jackson 2 now.
Merge #137
Closes #136
Merge branch 'split-aws-java-sdk' of https://github.com/Collaborne/elasticsearch-cloud-aws into Collaborne-split-aws-java-sdk
Update AWS SDK to 1.9.8

Closes #148