upgrade denominator to 1.2.0: supports duplicate zone names

DNS providers like Amazon Route53 and Rackspace CloudDNS allow you to create multiple zones with the same name.  This is useful for testing, or having different results for internal vs external dns resolution.

The CLI `zone list` command now prints out zone ids when present.

```bash
$ denominator -p route53 -c AAAA -c SSSS zone list
myzone.com. Z3I0BTR7N27QRM
adrianc.zone.route53test.jclouds.org. Z1KWEIO71EBZIB
adrianc.zone.route53test.jclouds.org. ZO6XA7CYZ0IBA
dyntest.netflix.net. Z1VO4BIB35Q8HU
```

The CLI `-z` argument can be either a zone name or id.  If the provider supports multiple zones with the same name, and you specify the zone name instead of its id, there will be a slight lag as the first zone is looked up.
```bash
$ denominator -p route53 -c AAAA -c SSSS record -z adrianc.zone.route53test.jclouds.org. list
adrianc.zone.route53test.jclouds.org.             NS     172800ns-927.awsdns-51.net.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-1875.awsdns-42.co.uk.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-1051.awsdns-03.org.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-206.awsdns-25.com.
adrianc.zone.route53test.jclouds.org.             SOA    900   ns-927.awsdns-51.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
$ denominator -p route53 -c AAAA -c SSSS record -z ZO6XA7CYZ0IBA list
adrianc.zone.route53test.jclouds.org.             NS     172800ns-1850.awsdns-39.co.uk.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-1270.awsdns-30.org.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-920.awsdns-51.net.
adrianc.zone.route53test.jclouds.org.             NS     172800ns-39.awsdns-04.com.
adrianc.zone.route53test.jclouds.org.             SOA    900   ns-1850.awsdns-39.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
```