title: radio button directive not binding the ngModel
body: <p>i am trying to create a generic radioButton directive which will take options from controller for display:</p>
  
  <pre><code>&lt;cs-radio-field options="gender" ng-model="genderValue"&gt;&lt;/cs-radio-field&gt;
  </code></pre>
  
  <p>and the options would be like</p>
  
  <pre><code>$scope.gender = { label: "Gender", required:true,  valueList: [{ text: "Male", value: "yes" },{text:"Female", value:"no"}] };
  </code></pre>
  
  <p>the directive is defined as:</p>
  
  <pre><code>app.directive("csRadioField", function () {
      var templateHtml = function () {
          return '&lt;div ng-form="myform"&gt;' +
                  '&lt;div class="control-group" class="{{options.class}}"&gt;' +
                      '&lt;div class="control-label"&gt;{{options.label || "Radio"}} {{ options.required ? "*" : ""}} &lt;/div&gt;' +
                      '&lt;div class="controls"&gt;' +
                          '&lt;div class="radio" ng-repeat="(key, option) in options.valueList"&gt;' +
                              '&lt;label&gt; &lt;input type="radio" name="myfield" ng-value="option.value" ng-model="ngModel" ng-required="options.required" /&gt;{{option.text}} &lt;/label&gt;' +
                          '&lt;/div&gt;' +
                          '&lt;div class="field-validation-error" data-ng-show="myform.myfield.$invalid &amp;&amp; myform.myfield.$dirty"&gt; ' +
                              '&lt;div data-ng-show="myform.myfield.$error.required"&gt;{{options.label}} is required!!!&lt;/div&gt;' +
                          '&lt;/div&gt;' +
                      '&lt;/div&gt;' +
                  '&lt;/div&gt;' +
              '&lt;/div&gt;';
      };
  
      return {
          scope: { options: '=', ngModel: '=' },
          required: ['ngModel', '^form'],
          restrict: 'E',
          template: templateHtml,
      };
  });
  </code></pre>
  
  <p>but the ngModel is not binding in the parent scope.. mostly because of new scopes being created by ng-repeat.</p>
  
  <p>how to solve this issue?</p>
  
  <p>the plunker link: <a href="http://plnkr.co/edit/myS5hXwxjoDEqQI2q5Q7?p=preview" rel="nofollow" title="plunkr link">http://plnkr.co/edit/myS5hXwxjoDEqQI2q5Q7?p=preview</a></p>