Undo feature for language selection

* Use jQuery tipsy plugin to show previous language
* previous language is stored in cookie

Change-Id: Iaae668c33209e32a74dee00211bb22c7b3562456

UniversalLanguageSelector.php

@@ -68,6 +68,7 @@ $wgResourceModules['ext.uls.init'] = array(
 	'remoteExtPath' => 'UniversalLanguageSelector',
 	'dependencies' => array(
 		'mediawiki.Uri',
+		'jquery.tipsy',
 		'ext.uls.core',
 	),
 	'position' => 'top',