⬆️ Update HTML Purifier library.

Updated HTML Purifier from 4.6.0 to 4.9.2 with better PHP7 compatibility.
Used composer to manage this library.

vendor/composer/installed.json

@@ -634,5 +634,54 @@
             "oauth",
             "oauth2"
         ]
+    },
+    {
+        "name": "ezyang/htmlpurifier",
+        "version": "v4.9.2",
+        "version_normalized": "4.9.2.0",
+        "source": {
+            "type": "git",
+            "url": "https://github.com/ezyang/htmlpurifier.git",
+            "reference": "6d50e5282afdfdfc3e0ff6d192aff56c5629b3d4"
+        },
+        "dist": {
+            "type": "zip",
+            "url": "https://api.github.com/repos/ezyang/htmlpurifier/zipball/6d50e5282afdfdfc3e0ff6d192aff56c5629b3d4",
+            "reference": "6d50e5282afdfdfc3e0ff6d192aff56c5629b3d4",
+            "shasum": ""
+        },
+        "require": {
+            "php": ">=5.2"
+        },
+        "require-dev": {
+            "simpletest/simpletest": "^1.1"
+        },
+        "time": "2017-03-13T06:30:53+00:00",
+        "type": "library",
+        "installation-source": "dist",
+        "autoload": {
+            "psr-0": {
+                "HTMLPurifier": "library/"
+            },
+            "files": [
+                "library/HTMLPurifier.composer.php"
+            ]
+        },
+        "notification-url": "https://packagist.org/downloads/",
+        "license": [
+            "LGPL"
+        ],
+        "authors": [
+            {
+                "name": "Edward Z. Yang",
+                "email": "admin@htmlpurifier.org",
+                "homepage": "http://ezyang.com"
+            }
+        ],
+        "description": "Standards compliant HTML filter written in PHP",
+        "homepage": "http://htmlpurifier.org/",
+        "keywords": [
+            "html"
+        ]
     }
 ]