added docker-compose to start tornado backend and react frontend service

# .

services:

  react-frontend:

    build:

      context: ./react-frontend

    volumes:

      - ./react-frontend/my-react-app:/app

    ports:

      - "3000:3000"

    stdin_open: true

    tty: true

    environment:

      - CHOKIDAR_USEPOLLING=true # To support live reloading on mounted volumes

    command: ["npm", "start"]

    depends_on:

      - tornado-backend

  tornado-backend:

    build: ./tornado-backend

    links:

      - postgres

    ports:

      - "8888:8888"

    command: --db_host=postgres

  postgres:

    image: postgres:10.3

    environment:

      POSTGRES_USER: blog

      POSTGRES_PASSWORD: blog

      POSTGRES_DB: blog

    ports:

      - "5432:5432"