Fixes maxpou#32, linking containers is obsolete in version 2 docker-compose (maxpou#35)

* Fixes maxpou#32, linking containers is obsolete when using version 2 of docker compose. A network will be created between the containers to find each other.

* Changed README due to the named alias change

Author: leroy0211

README.md

@@ -40,7 +40,7 @@ Docker-symfony gives you everything you need for developing Symfony application.
         ```yml
         # path/to/your/symfony-project/app/config/parameters.yml
         parameters:
-            database_host: mysqldb
+            database_host: db
         ```
 
     2. Composer install & create database

docker-compose.yml

@@ -14,17 +14,13 @@ services:
         build: php7-fpm
         ports:
             - 9000:9000
-        links:
-            - db:mysqldb
         volumes:
             - ${SYMFONY_APP_PATH}:/var/www/symfony
             - ./logs/symfony:/var/www/symfony/app/logs
     nginx:
         build: nginx
         ports:
             - 80:80
-        links:
-            - php
         volumes_from:
             - php
         volumes: