title: <ion-nav-buttons/> doesn't work with isolated scope
body: <p>I'm trying to minimize my use of <code>$scope</code> as much as possible in an app I'm working on.  In this app, I can't get my nav-bar buttons to work with <code>ctrl</code> (using <code>controllerAs</code>) unless I don't use an isolated scope.</p>
  
  <p>CodePen: <a href="http://codepen.io/rinogo/pen/GjkPdG" rel="nofollow">http://codepen.io/rinogo/pen/GjkPdG</a></p>
  
  <p>As you can see, with an isolated scope (e.g. <code>scope: {}</code>), only the buttons that are not in the nav bar work.  However, if we comment out <code>scope: {}</code> and inherit the scope prototypally instead, all <em>four</em> buttons work.</p>
  
  <p>I can get the "scope method" to work in the nav-bar if I set <code>test()</code> on <code>$scope.$parent</code> instead.  Given the structure of my app, that's essentially <code>$rootScope</code> (aka the scope in which the <code>&lt;ion-nav-bar/&gt;</code> is present), right?</p>
  
  <p>It almost seems as if <code>&lt;ion-nav-buttons/&gt;</code> is evaluated in the scope of the related <code>&lt;ion-nav-bar/&gt;</code> instead of the scope in which it is defined!  Perhaps this also explains why the <code>ctrl</code> approach only works with inherited scope, since "behind the scenes" <code>ctrl</code> is accessed via the <code>$scope.ctrl</code>, right?</p>
  
  <p>So I guess my questions are:</p>
  
  <ol>
  <li>Is <code>&lt;ion-nav-buttons/&gt;</code> evaluated in the scope of the related <code>&lt;ion-nav-bar/&gt;</code>?</li>
  <li>If so, why?</li>
  <li>How can I accomplish my goal of calling <code>ctrl.test()</code> from <code>ng-click</code> in <code>&lt;ion-nav-buttons/&gt;</code> (while retaining an isolated scope)?</li>
  </ol>
  
  <p>Thanks in advance for sharing your expertise! :)</p>