docs(ngJq): update to indicate common pitfall

src/Angular.js

@@ -964,10 +964,10 @@ var csp = function() {
  * used to force either jqLite by leaving ng-jq blank or setting the name of
  * the jquery variable under window (eg. jQuery).
  *
- * Since this directive is global for the angular library, it is recommended
- * that it's added to the same element as ng-app or the HTML element, but it is not mandatory.
- * It needs to be noted that only the first instance of `ng-jq` will be used and all others
- * ignored.
+ * Since angular looks for this directive when it is loaded (doesn't wait for the
+ * DOMContentLoaded event), it must be placed on an element that comes before the script
+ * which loads angular. Also, only the first instance of `ng-jq` will be used and all
+ * others ignored.
  *
  * @example
  * This example shows how to force jqLite using the `ngJq` directive to the `html` tag.