Use public ip and hostname for host lookup. Fixes infochimps-labs/ironfan#328
fix: Use public ip and hostname for host lookup.

Merge remote-tracking branch 'travis/cluster_kick'

This fix allows maps IP addresses to Ironfan names for display by the
cluster_ssh plugin. It addresses the following pull request:
https://github.com/infochimps-labs/ironfan/pull/329.