New option for route53: retry_interval

The current (hard-coded) retry interval of 500 seconds can cause ansible to have excessive run-times in the case of many domains. `retry_interval` provides a way to customize the wait between retries of calls to route53.
Merge branch 'patch-2' of https://github.com/napkindrawing/ansible into napkindrawing-patch-2
Merge branch 'napkindrawing-patch-2' into devel