docs(ionicBar, ionicNavBar): add ng-click to usage example

js/ext/angular/src/directive/ionicBar.js

@@ -60,7 +60,7 @@ angular.module('ionic.ui.header', ['ngAnimate', 'ngSanitize'])
  * ```html
  * <ion-header-bar align-title="left" class="bar-positive">
  *   <div class="buttons">
- *     <button class="button">Left Button</button>
+ *     <button class="button" ng-click="doSomething()">Left Button</button>
  *   </div>
  *   <h1 class="title">Title!</h1>
  *   <div class="buttons">
@@ -103,7 +103,7 @@ angular.module('ionic.ui.header', ['ngAnimate', 'ngSanitize'])
  *     <button class="button">Left Button</button>
  *   </div>
  *   <h1 class="title">Title!</h1>
- *   <div class="buttons">
+ *   <div class="buttons" ng-click="doSomething()">
  *     <button class="button">Right Button</button>
  *   </div>
  * </ion-footer-bar>

js/ext/angular/src/directive/ionicNavBar.js

@@ -362,7 +362,7 @@ function($ionicViewService, $rootScope, $animate, $compile, $parse) {
  * <ion-nav-view>
  *   <ion-view>
  *     <ion-nav-buttons side="left">
- *       <button class="button">
+ *       <button class="button" ng-click="doSomething()">
  *         I'm a button on the left of the navbar!
  *       </button>
  *     </ion-nav-buttons>