Add mobile push API
Add unit tests for publish operation
Add target_arn to publish method in SNS client
Updated Redshift for ``copy_cluster_snapshot/delete_cluster_snapshot`` changes.
Moved EMR to SigV4.
Updated SNS docs.
Merge branch 'emr-sigv4' into develop
Merge branch 'redshift-updates' into develop
Merge branch 'sns-mobile-push' into develop
Added release notes for v2.10.0.
Bumping version to 2.10.0
Merge branch 'release-2.10.0' into develop

* release-2.10.0:
  Bumping version to 2.10.0