add aws-sdk gem
add aws.yml structure
add a column to track the SNS ARN
add mechanism to publish entity changes
pretty sure this is unnecessary
modernize hash literals

convert string keys to symbols, and “:key => value” syntax to “key: value”
add a small rake task to “live-test” EntityUpdatePublisher

* verifies credentials in aws.yml
* verifies EntityUpdatePublisher’s usage of the aws-sdk
test the after_rollback hook
define the change message (json)
change publication strategy

Instead of using a thread-local to track publications, we now only allow the root entity to emit a publication, and we now guarantee the root entity is always changed if any of its descendants is changed.
add a rake task to add topics to root entity types
SNS topic arn needs to get saved to the db