Require PHPUnit 4.8.36

To ensure we have the forward compatibility layer (for PHPUnit 6+).

Author: lcobucci

composer.json

@@ -26,7 +26,7 @@
         "doctrine/migrations": "^1.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.8"
+        "phpunit/phpunit": "^4.8.36"
     },
     "autoload": {
         "psr-4": { "Doctrine\\Bundle\\MigrationsBundle\\": "" }