Update dependencies.

* php >=7.2
* phpunit ^8.0

Author: TiSiE

composer.json

@@ -14,8 +14,8 @@
     "optimize-autoloader": false
   },
   "require": {
-    "php": ">=7.1",
-    "phpunit/phpunit": "^5.7"
+    "php": ">=7.2",
+    "phpunit/phpunit": "^8.0"
   },
   "autoload": {
     "psr-4": {