Release Docker images upon tag pushed

[alexellis]

• Upon successful builds, release a Docker image with the corresponding tag.

This should cover openfaas/faas, openfaas/faas-netes and openfaas/nats-queue-worker ideally via Travis or Docker Hub.

[burtonr]

Hi Alex,
I'm just started using this project and would love to help out for Hacktoberfest!

Just to be sure I know what you're expecting here, you want Travis-CI to push a docker image with the git commit tag as the image tag to Docker Hub.

Would you want also want a :latest tag as well?

For the other projects, faas-netes and nats-queue-worker, are you going to open issues on each of those projects for this same update so the PR can be matched up, or if you'd like, I could do that.

[burtonr]

We can close this as PR #254 has been merged

[alexellis]

Derek close

[alexellis]

@burtonr please close issues using Derek