More intro Docker stuff

Over the past half hour, I learned to write a recipe for building an image called the Dockerfile. I then told Docker to make a cake called an image with the docker build command. I then told it to throw a party around this cake, to run a container. I made some changes to some files (to something the recipe uses) and rebaked the cake. The old party was using a room that I wanted, so I stopped the old party (stopped running the container) to free up that room (the 3000 port), and I threw a new party (ran the new container) with that cake in the center.