New phpunit version constraint

DivineOmega · DivineOmega · commit 7b9773495980 · 2018-05-07T20:27:39.000+01:00
diff --git a/composer.json b/composer.json
@@ -8,7 +8,7 @@
     },
     "require-dev": {
         "orchestra/testbench": "~3.0",
-        "phpunit/phpunit": "^6.0",
+        "phpunit/phpunit": ">=5.0",
         "satooshi/php-coveralls": "^2.0"
     },
     "license": "LGPL-3.0-only",
