Added fixed PHP version in composer.json

Author: WyriHaximus

composer.json

@@ -39,7 +39,10 @@
         }
     },
     "config": {
-        "sort-packages": true
+        "sort-packages": true,
+        "platform": {
+          "php": "7.0"
+        }
     },
     "scripts": {
         "ensure-installed": "composer install --ansi -n -q",