Nginx official image

Shouldn't we use the official nginx image instead of building one from debian:jessie ? We could use something like:

services:
# ...
  nginx:
    image: nginx:1.13
    depends_on:
      - php
    volumes:
      - ${SYMFONY_APP_PATH}/web/:/var/www/symfony/web
      - ./logs/nginx:/var/logs/nginx
      - ./symfony.conf:/etc/nginx/conf.d/default.conf
# ...

No Dockerfile is even needed for the service

Hi, Your proposal looks good :) Feel free to open a PR!