anchor.diff:  ## Removing the image goes like this:
   # docker rmi punchcardjs-image
   
  -# start from Node's offical docker image, version 4.5 (https://hub.docker.com/r/library/node/)
  -FROM node:4.5
  +# start from Node's offical docker image, version 7.0 (https://hub.docker.com/r/library/node/)
  +FROM node:7.0
   
   # open network port (at outside of the container)
   EXPOSE 5000
  
positive.code: RUN apt-get install -y git
  
  # get a copy of the repository
  RUN git clone https://github.com/nlesc-sherlock/punchcardjs-demo.git
  
  # change into the directory
  WORKDIR /punchcardjs-demo
  
  # Be explicit about which branch we're using
  RUN git checkout master
  
  # install the dependencies listed in package.json
  RUN npm install
  
negative.code: ## First install docker on your machine
  ## Then you can build the docker image with this command (the build looks
  ## in the current file):
  # docker build -t image-punchcardjs-demo .
  ## Then run the docker container using this command:
  # docker run -p 5001:5000 --name prosperous-punchcards image-punchcardjs-demo
  