Nightly releases of eventing

[adrcunha]

Expected Behavior

Latest, tagged release-eventing.yaml is available nightly.

Actual Behavior

This doesn't happen. :)

[adrcunha]

#168 created the release script.

[adrcunha]

Job created, first release cut (manually):

https://storage.googleapis.com/knative-releases/previous/v20180711-0a4b408-dirty/release-eventing.yaml