docs(select): add callout style for a note

src/ng/directive/select.js

@@ -28,10 +28,12 @@ var ngOptionsMinErr = minErr('ngOptions');
  * be nested into the `<select>` element. This element will then represent the `null` or "not selected"
  * option. See example below for demonstration.
  *
- * Note: `ngOptions` provides iterator facility for `<option>` element which should be used instead
+ * <div class="alert alert-warning">
+ * **Note:** `ngOptions` provides iterator facility for `<option>` element which should be used instead
  * of {@link ng.directive:ngRepeat ngRepeat} when you want the
  * `select` model to be bound to a non-string value. This is because an option element can only
  * be bound to string values at present.
+ * </div>
  *
  * @param {string} ngModel Assignable angular expression to data-bind to.
  * @param {string=} name Property name of the form under which the control is published.
@@ -435,7 +437,7 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
 
           // We now build up the list of options we need (we merge later)
           for (index = 0; length = keys.length, index < length; index++) {
-            
+
             key = index;
             if (keyName) {
               key = keys[index];