Echo JS 0.11.0

React Forms uses immutable data (not so advanced as mori, just makes sure it doesn't mutate and produces a new copy on update). So that UndoMixin only works with immutable data.

Thanks for pointing this out n1k0!

You're welcome. Sample implementation outside of react-forms: 

- https://github.com/n1k0/kept/blob/master/src/js/mixins/UndoStack.js
- https://github.com/n1k0/kept/blob/master/src/js/components/KeptApp.jsx#L14-L29