Enhancement: Update phpunit/phpunit

Author: localheinz

composer.json

@@ -19,7 +19,7 @@
         "bjyoungblood/BjyProfiler": "1.1.0",
         "fabpot/php-cs-fixer": "~1.4",
         "fzaninotto/faker": "^1.4.0",
-        "phpunit/phpunit": "~4.5",
+        "phpunit/phpunit": "^4.8",
         "zendframework/zend-developer-tools": "dev-master",
         "zendframework/zftool": "dev-master"
     },