Incorrect tag checked

Merge pull request #21 from 030/16-tag

[GH-16] incorrect tag was checked

Throw exit1 if tagging or docker push fails

Merge pull request #20 from 030/16-error-handling

[GH-16] Throw error if docker tag or push fails

Preserve non-library images from docker hub

Merge pull request #19 from 030/18-other-images

18 other images

Throw Exit1 only registry lacks tag immutability

Merge pull request #15 from 030/14-false-positive

false positive

Preserve a docker image in a private registry

Merge pull request #13 from 030/1-preserve

1 preserve

Throw exit 1 if image already exists in a docker-registry

Merge pull request #12 from 030/11-tag-immutability

[GH-11] Throw an exit 1 if an image tag exists in a registry.

Check whether an image resides in a docker-registry

Merge pull request #10 from 030/gh2-auto-publish

[GH-2] Apparently stage should be called 'deploy' for auto publication