Included differences in readme

README.md

@@ -6,6 +6,17 @@ Rich tool tips in your TeachBook!
 
 Sphinx-tippy allows you to create rich hover over tips as demonstrated here: https://sphinx-tippy.readthedocs.io/en/latest/. This TeachBooks Tippy extension makes it plug-and-play within a TeachBook.
 
+The differences with Sphinx-tippy are:
+
+- Default inclusion of useful CSS-file.
+- Default activation of sphinx.ext.mathjax.
+- Default loading method of _defer_ changed to _None_ for supporting JavaScript.
+- Default support for [TeachBooks Sphinx Grasple](https://github.com/TeachBooks/Sphinx-Grasple-public) such that images are shown (as iframes are not loaded).
+
+Future differences with Sphinx-tippy are:
+
+- Addition of a directive _repeat_ to show content explicity. 
+
 ## What does it do?
 
 You can see how the this works in the [example book](https://teachbooks.io/TeachBooks-sphinx-tippy-Example).