building docker images to build docker images to build docker images

This builds a docker image that can be run with 4 environment variables:

• GIT_REPO_URL - The URL of a repo to check out
• DOCKER_REPO_NAME - the tag of the docker image you want to build from the repo
• OP_CONFIG_BUCKET - the s3 bucket location of an op config file
• OP_CONFIG_FILE (optional, defaults to op.cfg) - the file name of the op config file

The op config file should contain the following:

• DOCKERHUB_USER
• DOCKERHUB_EMAIL
• DOCKERHUB_PASSWORD
• DOCKER_TAG
• GITHUB_USER
• GITHUB_PASSWORD
• TEST_COMMAND