upgrade code to be used with PHP 7.3+

.gitignore

@@ -26,3 +26,9 @@ index
 
 # php_cs
 .php_cs.cache
+
+# composer
+composer.lock
+
+# php unit
+.phpunit.result.cache

composer.json

@@ -28,34 +28,30 @@
     "minimum-stability": "dev",
     "prefer-stable": true,
     "require": {
-        "yiisoft/yii2": "~2.0.5",
-        "bower-asset/chartjs": "~2.6"
+        "php": ">=7.3",
+        "yiisoft/yii2": "^2.0",
+        "nnnick/chartjs": "^2.9"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.4",
-        "friendsofphp/php-cs-fixer": "^2.0"
+        "roave/security-advisories": "dev-master",
+        "friendsofphp/php-cs-fixer": "^2.16",
+        "phpunit/phpunit": "^8.5"
     },
     "autoload": {
         "psr-4": {
             "dosamigos\\chartjs\\": "src"
         }
     },
-    "config": {
-        "fxp-asset": {
-            "installer-paths": {
-                "npm-asset-library": "vendor/npm",
-                "bower-asset-library": "vendor/bower"
-            },
-            "vcs-driver-options": {
-                "github-no-api": true
-            },
-            "git-skip-update": "2 days",
-            "pattern-skip-version": "(-build|-patch)"
-        }
-    },
     "extra": {
+        "installer-types": ["bower-asset", "npm-asset"],
         "branch-alias": {
             "dev-master": "1.0-dev"
         }
-    }
+    },
+    "repositories": [
+        {
+            "type": "composer",
+            "url": "https://asset-packagist.org"
+        }
+    ]
 }