Fix nested checkbox demo and update test name

Fixes #575.

Author: devversion

src/components/checkbox/checkbox.spec.ts

@@ -213,7 +213,7 @@ describe('MdCheckbox', () => {
       expect(testComponent.onCheckboxClick).toHaveBeenCalledTimes(1);
     });
 
-    it('should trigger the change event properly', async(() => {
+    it('should trigger a change event when the native input does', async(() => {
       spyOn(testComponent, 'onCheckboxChange');
 
       expect(inputElement.checked).toBe(false);

src/demo-app/checkbox/checkbox-demo.html

@@ -40,6 +40,5 @@ <h1>md-checkbox: Basic Example</h1>
   </div>
 </div>
 
-<h1>Application Example: Nested Checklist</h1>
-<h2><em>Caution: WIP!</em></h2>
-<md-checkbox-demo-nested-checklist></md-checkbox-demo-nested-checklist>
+<h1>Nested Checklist</h1>
+<md-checkbox-demo-nested-checklist></md-checkbox-demo-nested-checklist>

src/demo-app/checkbox/nested-checklist.html

@@ -4,7 +4,7 @@ <h2>Tasks</h2>
     <md-checkbox [(ngModel)]="task.completed"
                  [checked]="allComplete(task)"
                  [indeterminate]="someComplete(task.subtasks)"
-                 (change)="setAllCompleted(task.subtasks, $event)">
+                 (change)="setAllCompleted(task.subtasks, $event.checked)">
       <h3>{{task.name}}</h3>
     </md-checkbox>
     <ul>