Add Route53 Hosted Zone Trimming (#999)

* Add Route53 Hosted Zone Trimming

Route53 requires a customization where `/hostedzone/` is stripped from hosted zone arguments when round-tripped. This adds a trait and customization to the route53 model to trim hosted zone prefixes.

* Add missing copyright header

* Also allow no leading slash

* Add route53 to smoke test because it has unit tests

* Update changelog

* Add missing call to flush()

* Remove unused env_logger depedendency