Update dependencies

* github.com/cloudfoundry/storeadapter
* github.com/cloudfoundry/gunk (necessitated by above)
* github.com/stretchr/testify (to ensure compatibility on Travis)
* fallout from updating dependencies

[#81719084]

Signed-off-by: John Tuley <jtuley@pivotal.io>
Add Elector for syslog_drain_binder

[#81719084]

Signed-off-by: John Tuley <jtuley@pivotal.io>
Return *Elector from elector.NewElector

[#81719084]

Signed-off-by: John Tuley <jtuley@pivotal.io>
Add cloud_controller_poller.Poll

[#81719084]

Signed-off-by: John Tuley <jtuley@pivotal.io>