This commit exports the `arn` as well as the `id`, since IAM
roles require the full resource name rather than just the table
name. I'd even be in favor or having `arn` as the `id` since the
<region, tablename> pair is the uniqueness constraint, but this
will keep backwards compatibility:
http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_CreateTable.html