Webpack (#1367)

* Replace gulp with webpack and npm scripts for JS compilation
* Set up Travis CI to commit compiled JS
* Restructure `js` directory; only one instance of npm, forum/admin are "submodules"
* Refactor JS initializers into Application subclasses
* Maintain partial compatibility API (importing from absolute paths) for extensions
* Remove minification responsibility from PHP asset compiler
* Restructure `less` directory

js/src/forum/components/LoadingPost.js

@@ -0,0 +1,25 @@
+import Component from '../../common/Component';
+import avatar from '../../common/helpers/avatar';
+
+/**
+ * The `LoadingPost` component shows a placeholder that looks like a post,
+ * indicating that the post is loading.
+ */
+export default class LoadingPost extends Component {
+  view() {
+    return (
+      <div className="Post CommentPost LoadingPost">
+        <header className="Post-header">
+          {avatar(null, {className: 'PostUser-avatar'})}
+          <div className="fakeText"/>
+        </header>
+
+        <div className="Post-body">
+          <div className="fakeText"/>
+          <div className="fakeText"/>
+          <div className="fakeText"/>
+        </div>
+      </div>
+    );
+  }
+}