Bash script to push versioned images to docker hub
The script will push the image if the env TRAVIS_GO_VERSION matches the GO_FOR_RELEASE.
If on master => pushes to latest.
If it's a tag in the format 1.2.3 => pushes to v1.2.3 and v1
If it's a tag in the format 1.2.3-rc => pushes to v1.2.3-rc
IMAGE_NAME: image name, in the format, repo/name, to be used when pushing the image.