[1.8.x] 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.

Backport of f9de197268 from master

docs/ref/csrf.txt

@@ -114,12 +114,12 @@ 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::