code review :)

* removes the state duplication (it only exists at the top level now);
* the only component that also holds state is the form, that needs it to hold the unsaved state of the input area field;
* add ids to the data (so that React can properly update/add/remove) nodes;
* some changes in the naming convention: uses handle to any function that is an event handler :)
* renames everybody to sections (just because, hehe)
* adds underscore for laziness (I wanted an easy way to do a find).

These are my two cents, given my small experience with React.

Hope it helps you.