This editor is now used in http://classfoo.com/. It's totally based on wysihtml5 and beautified by BootStrap, FontAwesome and JQuery.All honors belong to their original authors.Enjoy it!
Online example: http://classfoo.com/app/editor
Core parts: wysihtml5 https://github.com/xing/wysihtml5 bootstrap https://github.com/twbs/bootstrap font awesome http://fontawesome.io/ JQuery http://jquery.com/
Heads up! Wysihtml5 isn’t maintained anymore, but we have already tried to modify some of it's bugs and keep it following the contemporary browers.Of course, we will keep doing this in the near future.