Merge pull request #7 from shochdoerfer/feature/phpunit_update

Migrate to PHPUnit 6.x

Author: shochdoerfer

composer.json

@@ -21,7 +21,7 @@
     "sensiolabs/security-checker": "^4.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^4.8",
+    "phpunit/phpunit": "^6.0",
     "squizlabs/php_codesniffer": "^2.3",
     "phpdocumentor/phpdocumentor": "^2.8"
   },