refactor(rating): use track by in template

Closes #1724

template/rating/rating.html

@@ -1,5 +1,5 @@
 <span ng-mouseleave="reset()" ng-keydown="onKeydown($event)" tabindex="0" role="slider" aria-valuemin="0" aria-valuemax="{{range.length}}" aria-valuenow="{{value}}">
-    <i ng-repeat="r in range" ng-mouseenter="enter($index + 1)" ng-click="rate($index + 1)" class="glyphicon" ng-class="$index < value && (r.stateOn || 'glyphicon-star') || (r.stateOff || 'glyphicon-star-empty')">
+    <i ng-repeat="r in range track by $index" ng-mouseenter="enter($index + 1)" ng-click="rate($index + 1)" class="glyphicon" ng-class="$index < value && (r.stateOn || 'glyphicon-star') || (r.stateOff || 'glyphicon-star-empty')">
         <span class="sr-only">({{ $index < value ? '*' : ' ' }})</span>
     </i>
 </span>