title: Can't reset form with '$setPristine'
body: <p>I get an error when I run the following code to reset my form:</p>
  
  <pre><code> $scope.saveFormData = function () {
              $scope.testForm.$setPristine();
  }
  </code></pre>
  
  <p>And HTML:</p>
  
  <pre><code>&lt;form name="testForm" &gt;
  
                  &lt;label class="item item-input item-stacked-label"&gt;
                      &lt;span class="input-label"&gt;Title&lt;/span&gt;
                      &lt;input type="text" ng-model="formData.shortDesc" required=""&gt;
                  &lt;/label&gt;
   &lt;button class="button button-block button-positive" type="submit" ng-click="saveFormData()" &gt;Opslaan &lt;/button&gt;
  
  &lt;/form&gt;
  </code></pre>