Update dependencies (#200)

- Update the dependencies
- Upgrade from PHPUnit 6 to PHPUnit 7

Author: theofidry

composer.json

@@ -28,7 +28,7 @@
     },
     "require-dev": {
         "bamarni/composer-bin-plugin": "^1.1",
-        "phpunit/phpunit": "^6.1"
+        "phpunit/phpunit": "^7.0"
     },
 
     "bin": ["bin/php-scoper"],