Updated PHPUnit to 7.0

Author: michalbundyra

composer.json

@@ -27,7 +27,7 @@
         "psr/http-server-middleware": "^1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^6.5.5",
+        "phpunit/phpunit": "^7.0.2",
         "roave/security-advisories": "dev-master",
         "zendframework/zend-coding-standard": "~1.0.0"
     },