chore: add composer script

Author: adhocore

composer.json

@@ -27,5 +27,9 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8 || ^5.7 || ^6.5"
+    },
+    "scripts": {
+        "test": "vendor/bin/phpunit",
+        "test:cov": "vendor/bin/phpunit --coverage-text --coverage-clover coverage.xml"
     }
 }