Fix dependency

Author: sebastianbergmann

composer.json

@@ -29,7 +29,7 @@
         "sebastian/version": ">=1.0.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "3.8.*@dev",
+        "phpunit/phpunit": "3.9.*@dev",
         "ext-xdebug": ">=2.2.1"
     },
     "suggest": {