Revert Kibana upgrade

Kibana 3.0.1 depends on elasticsearch 0.90.0. We are currently on
0.20.6. Upgrading elasticsearch would be quite a bit of work for no
discernable gain and there are no new features in Kibana that we
absolutely need so I'm rolling this back.
Merge pull request #370 from alphagov/revert-kibana-upgrade

Revert Kibana upgrade