Add Docker readme to docker folder

Author: mdmintz

docker/Docker_README.md

@@ -0,0 +1,59 @@
+## Docker setup instructions for SeleniumBase
+
+#### 1. Get the Docker Toolbox from https://www.docker.com/docker-toolbox and install it.
+
+#### 2. Create your SeleniumBase Docker environment:
+
+    docker-machine create --driver virtualbox seleniumbase
+
+#### 3. If your Docker environment ever goes down for any reason, you can bring it back up with a restart:
+
+    docker-machine restart seleniumbase
+
+#### 4. Configure your shell:
+
+    eval "$(docker-machine env seleniumbase)"
+
+#### 5. Go to the SeleniumBase home directory. (That's where "Dockerfile" is located)
+
+#### 6. Create your Docker image from your Dockerfile: (Get ready to wait awhile)
+
+    docker build -t seleniumbase .
+
+#### 7. Run a test inside your Docker: (Once the test completes after a few seconds, you'll automatically exit the Docker shell)
+
+    docker run seleniumbase ./run_docker_test_in_firefox.sh
+
+#### 8. You can also enter Docker and stay inside the shell:
+
+    docker run -i -t seleniumbase
+
+#### 9. Now you can run the example test from inside the Docker shell: (This time using PhantomJS)
+
+    ./run_docker_test_in_phantomjs.sh
+
+#### 10. When you're satisfied, you may exit the Docker shell:
+
+    exit
+
+#### 11. (Optional) Since Docker images and containers take up a lot of space, you may want to clean up your machine from time to time when they’re not being used:
+http://stackoverflow.com/questions/17236796/how-to-remove-old-docker-containers
+Here are a few of those cleanup commands:
+
+    docker images | grep "<none>" | awk '{print $3}' | xargs docker rmi
+    docker rm 'docker ps --no-trunc -aq'
+
+If you want to completely remove all of your Docker containers and images, use these commands: (If there's nothing to delete, those commands will return an error.)
+
+    docker rm $(docker ps -a -q)
+    docker rmi $(docker images -q)
+
+Finally, if you want to wipe out your SeleniumBase Docker virtualbox, use these commands:
+
+    docker-machine kill seleniumbase
+    docker-machine rm seleniumbase
+
+#### 12. (Optional) More reading on Docker can be found here:
+* https://docs.docker.com
+* https://docs.docker.com/mac/started/
+* https://docs.docker.com/installation/mac/