Fixed setup image version, Enterprise installation support

This was previously 7.0 which lacked support for the M2SETUP_USE_COMPOSER_ENTERPRISE variable, and also didn't match the image version in use for phpfpm.

docker-compose.yml

@@ -37,7 +37,7 @@ dbdata:
     - /var/lib/mysql
 
 setup:
-  image: mageinferno/magento2-php:7.0-fpm-0
+  image: mageinferno/magento2-php:7.1-fpm-0
   command: /usr/local/bin/mage-setup
   links:
     - db