Change TTL of generated records to 10 minutes

Usually an IP for a node will not change, so a long TTL is desired. The
exception is if we assign an elastic IP to a node. In these cases, however
rare, we would like the change to propagate sooner than 24 hours.
Merge pull request #15 from airbnb/ttl-10-mins

Change TTL of generated records to 10 minutes