Require phpunit

Author: snapshotpl

composer.json

@@ -16,7 +16,7 @@
         "http-interop/http-middleware": "^0.4.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.6 || ^6.1.3",
+        "phpunit/phpunit": "^5.7.27 || ^6.1.3",
         "ramsey/uuid": "^3.0",
         "zendframework/zend-diactoros": "^1.1.3"
     },