the current update frequency for the refresh loop in the route 53 plugin is hard-coded
to 1 minute. aws rate-limits the number of api requests so less frequent record refreshes
can help when reaching those limits depending upon your individual scenarios. this pull
adds a configuration option to the route53 plugin to adjust the refresh frequency.

thanks for getting my last pull released so quickly. this is the last local change that
i have been running and would love to get it contributed back to the project.
Signed-off-by: Matt Kulka <mkulka@parchment.com>