added InstanceMetadataHook so that downstream modules can use it to access variables present in ec2 instances
added default slf4j module to avoid spamming console
refactored route53 to use InstanceMetadataHook
issue #23: add ec2 shortcuts to supply A or CNAME record data from instance metadata
Merge pull request #74 from Netflix/ec2-cli-hooks

issue #23: add ec2 shortcuts to supply A or CNAME record data from instance metadata