Update composer

composer.json

@@ -11,7 +11,7 @@
         "psr-4": { "Tests\\": "tests/" }
     },
     "require": {
-        "php": ">=5.5.9",
+        "php": ">=7.0",
         "symfony/symfony": "3.2.*",
         "doctrine/orm": "^2.5",
         "doctrine/doctrine-bundle": "^1.6",
@@ -29,12 +29,13 @@
         "knplabs/knp-paginator-bundle": "^2.5",
         "lexik/form-filter-bundle": "~5.0",
         "liip/imagine-bundle": "^1.7",
-        "maennchen/zipstream-php": "^0.4.0"
     },
     "require-dev": {
         "sensio/generator-bundle": "^3.0",
-        "symfony/phpunit-bridge": "^3.0",
-        "friendsofphp/php-cs-fixer": "^2.0"
+        "symfony/phpunit-bridge": "3.3.*@dev",
+        "phpunit/phpunit": "^6.1",
+        "friendsofphp/php-cs-fixer": "^2.0",
+        "mikey179/vfsStream": "^1.6"
     },
     "scripts": {
         "symfony-scripts": [
@@ -52,11 +53,6 @@
             "@symfony-scripts"
         ]
     },
-    "config": {
-        "platform": {
-            "php": "5.5.9"
-        }
-    },
     "extra": {
         "symfony-app-dir": "app",
         "symfony-bin-dir": "bin",