title: $mdDialog not working
body: <p><code>$mdDialog</code> not working with custom template.
  here's the code:</p>
  
  <p>HTML:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;md-button class="md-icon-button" ng-click="commentPrompt($event)"&gt;
    &lt;p&gt;button
    &lt;/p&gt;
  &lt;/md-button&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>JS:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code> var app = angular.module('BetaApp', ['ngMaterial', 'firebase']);
   
      
      app.controller('SideNavController', function($scope, $mdDialog) {
   $scope.commentPrompt = showDialog;
  function showDialog($event){
    var parentEl = angular.element(document.body);
    $mdDialog.show({
           parent: parentEl,
           targetEvent: $event,
           templateUrl: 'comment.html',
           controller: DialogController
        });
   };
   function DialogController($scope, $mdDialog) {
          $scope.closeDialog = function() {
            $mdDialog.hide();
          }
      }
  });</code></pre>
  </div>
  </div>
  </p>
  
  <p>COMMENT.HTML:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code> &lt;md-dialog&gt;
  &lt;span&gt;test
  &lt;/span&gt;
  &lt;md-button ng-click="closeDialog()" class="md-primary"&gt;
    &lt;p&gt;close&lt;/p&gt;
    &lt;/md-button&gt;
  &lt;/md-dialog&gt;</code></pre>
  </div>
  </div>
  </p>