Show close button regardless of onChange callback being provided.

Author: g1eb

src/datetime-range.html

@@ -82,7 +82,7 @@
         <div class="arrow arrow-down" ng-click="setDate(selected.clone().subtract(1, 'seconds'))"></div>
       </div>
     </div>
-    <div class="close-button" ng-if="!!onClose">
+    <div class="close-button">
       <div ng-click="close()">Close</div>
     </div>
   </div>