6: Upgrade PHPUnit dependencies

- PHPUnit -> ~7.0.0
- PHPCPD -> ~4.0.0

Author: mikeymike

composer.json

@@ -84,8 +84,8 @@
         "lusitanian/oauth": "~0.8.10",
         "pdepend/pdepend": "2.5.2",
         "phpmd/phpmd": "@stable",
-        "phpunit/phpunit": "~6.2.0",
-        "sebastian/phpcpd": "~3.0.0",
+        "phpunit/phpunit": "~7.0.0",
+        "sebastian/phpcpd": "~4.0.0",
         "squizlabs/php_codesniffer": "3.2.2"
     },
     "replace": {