Recommended the JavaScript Cookie library instead of jQuery cookie.

jQuery cookie is no longer maintained in favor of the JavaScript
cookie library. This also removes the jQuery dependency.

docs/ref/csrf.txt

@@ -117,12 +117,12 @@ Acquiring the token is straightforward:
     }
     var csrftoken = getCookie('csrftoken');
 
-The above code could be simplified by using the `jQuery cookie plugin
-<http://plugins.jquery.com/cookie/>`_ to replace ``getCookie``:
+The above code could be simplified by using the `JavaScript Cookie library
+<https://github.com/js-cookie/js-cookie/>`_ to replace ``getCookie``:
 
 .. code-block:: javascript
 
-    var csrftoken = $.cookie('csrftoken');
+    var csrftoken = Cookies.get('csrftoken');
 
 .. note::