chore: rename modules/examples to modules/playground

The directory contains code authored in a style that makes it transpilable to dart. As such, these are not idiomatic examples of Angular 2 usage.

The main purpose of this directory is to enable experimentation with Angular within the angular/angular repository.

Closes #4342

Closes #4639

modules/playground/src/zippy_component/index.ts

@@ -0,0 +1,25 @@
+import {bootstrap} from 'angular2/bootstrap';
+import {Component, View, NgFor} from 'angular2/core';
+import {Zippy} from './zippy';
+
+@Component({selector: 'zippy-app'})
+@View({
+  template: `
+    <zippy (open)="pushLog('open')" (close)="pushLog('close')" title="Details">
+      This is some content.
+    </zippy>
+    <ul>
+      <li *ng-for="var log of logs">{{log}}</li>
+    </ul>
+  `,
+  directives: [Zippy, NgFor]
+})
+class ZippyApp {
+  logs: string[] = [];
+
+  pushLog(log: string) { this.logs.push(log); }
+}
+
+export function main() {
+  bootstrap(ZippyApp);
+}