Create html-entities definitions file (#8890)

* Create html-entities definitions file

* Fix Travis test

html-entities/html-entities-tests.ts

@@ -0,0 +1,10 @@
+/// <reference path="html-entities.d.ts" />
+
+import * as htmlEntities from "html-entities";
+ 
+let entities = new htmlEntities.AllHtmlEntities();
+ 
+console.log(entities.encode('<>"\'&©®')); // &lt;&gt;&quot;&apos;&amp;©® 
+console.log(entities.encodeNonUTF('<>"\'&©®')); // &lt;&gt;&quot;&apos;&amp;&#169;&#174; 
+console.log(entities.encodeNonASCII('<>"\'&©®')); // <>"\'&©® 
+console.log(entities.decode('&lt;&gt;&quot;&apos;&amp;&copy;&reg;&#8710;')); // <>"'&&copy;&reg;∆

html-entities/html-entities.d.ts

@@ -0,0 +1,17 @@
+// Type definitions for html-entities v1.2.0
+// Project: https://www.npmjs.com/package/html-entities
+// Definitions by: Xavier Stouder <https://github.com/xstoudi/>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+declare module "html-entities" {
+    abstract class Entities {
+        encode(toEncode: string): string;
+        encodeNonUTF(toEncode: string): string;
+        encodeNonASCII(toEncode: string): string;
+        decode(toDecode: string): string;
+    }
+    class XmlEntities extends Entities {}
+    class Html4Entities extends Entities {}
+    class Html5Entities extends Entities {}
+    class AllHtmlEntities extends Entities {}
+}