Require PHP >= 7.2

- remove test on Composer v1
- remove deprecated function
- move `loadHtml()` into `init()` instead of `__construct`

Kinda prepare 2.0 version :)

composer.json

@@ -24,15 +24,17 @@
         "role": "Developer (original JS version)"
     }],
     "require": {
-        "php": ">=5.6.0",
+        "php": ">=7.2.0",
         "ext-mbstring": "*",
         "psr/log": "^1.0",
         "masterminds/html5": "^2.7"
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "^2.14",
+        "friendsofphp/php-cs-fixer": "^3.0",
         "monolog/monolog": "^1.24|^2.1",
-        "symfony/phpunit-bridge": "^4.4|^5.3"
+        "symfony/phpunit-bridge": "^4.4|^5.3|^6.0",
+        "phpstan/phpstan": "^1.3",
+        "phpstan/phpstan-phpunit": "^1.0"
     },
     "suggest": {
         "ext-tidy": "Used to clean up given HTML and to avoid problems with bad HTML structure."
@@ -42,5 +44,10 @@
     },
     "autoload-dev": {
         "psr-4": { "Tests\\Readability\\": "tests/" }
+    },
+    "config":{
+        "platform": {
+            "php": "7.2.34"
+        }
     }
 }