fix(input): support two way binding with value

 - name the output correctly
 - add json model to the form builder demo to demonstrate it in the examples page
 - closes #62

examples/components/input/form_builder.html

@@ -60,6 +60,8 @@ <h1>{{description}}</h1>
         </div>
       </md-input-container>
     </form>
+    <strong>Model</strong>
+    <pre class="md-padding">{{model | json}}</pre>
   </md-content>
 
 </div>

ng2-material/components/input/input.ts

@@ -46,7 +46,7 @@ export class MdInput {
 
   @Input()
   placeholder: string;
-  @Output()
+  @Output('valueChange')
   mdChange: EventEmitter<any> = new EventEmitter();
   @Output()
   mdFocusChange: EventEmitter<any> = new EventEmitter();