Fixed a NPE with v2 BatchGetItems

Fixed a NPE with v2 BatchGetItems, when no results.

Updated return value to be (more) consistent with the result from
DynamoDB.
Merge pull request #89 from itoshkov/fix/batch-get

Fixed a NPE with v2 BatchGetItems
incrementing version
[maven-release-plugin] prepare release alternator-0.9.2
[maven-release-plugin] prepare for next development iteration
releasing new version