Merge pull request #2 from php-elementary/phpunit

Allow new phpunit versions

Author: vendelev

composer.json

@@ -16,7 +16,7 @@
     },
     "require": {
         "php": ">=5.6",
-        "phpunit/phpunit": "^5.7",
+        "phpunit/phpunit": ">=5.7",
         "elementary/runtime-cache": "^1.0.0"
     }
 }