Creating a docker image for Saber #141

I'm not sure that a custom docker image is needed to build to saber sites. I would just use the default node images, install saber and then build it.

A few tutorials may be useful and/or templates may be helpful.

Basic config for circleci

version: 2
jobs:
  saber:
    docker:
      - image: circleci/node:10.8 # ...with this image as the primary container; this is where all `steps` will run
    steps:
      - checkout
      - run: npm install
      - run: 
          name: saber build
          command: |
            ls
            npx saber build

workflows:
  version: 2
  build_and_test:
    jobs:
      - saber

or even the base nodejs templates would be adequate.