issue #87: allow read commands of weighted record sets in route53

issue #87: allow read commands of weighted record sets in route53

tested offline and also with the cli (note multi-value CNAME)
```
$ denominator -p route53 -c XXX -c YYY record -z myzone.com. list -n fubar.myzone.com.
fubar.myzone.com.                                 CNAME  300   www1.myzone.com
fubar.myzone.com.                                 CNAME  300   www2.myzone.com
```