remove child factories

docs/09.1-animation.md

@@ -104,8 +104,6 @@ This is called when the `willEnter` `callback` is called.
 
 This is called when the child has been removed from the `ReactTransitionGroup`. Though the child has been removed, `ReactTransitionGroup` will keep it in the DOM until `callback` is called.
 
-Note that because the child has been removed you can no longer send it reactive updates. If you need this functionality, see the section on Child Factories below.
-
 ### `componentDidLeave()`
 
 This is called when the `willLeave` `callback` is called (at the same time as `componentWillUnmount`).
@@ -121,9 +119,3 @@ By default `ReactTransitionGroup` renders as a `span`. You can change this behav
 ```
 
 Every DOM component is under `React.DOM`. However, `component` does not need to be a DOM component. It can be any React component you want; even ones you've written yourself!
-
-### Advanced Feature: Child Factories
-
-`ReactTransitionGroup` is unique because when a child leaves `ReactTransitionGroup` it may stay in the DOM after the child is removed from the group. This means that you can't send it reactive updates anymore. If you need to send it updates, you can provide a `childFactory` callback prop which will take the original child instance (even after it has left the group) and return a React component to render in its place.
-
-Normally you do not need to think about this feature. If you do, the easiest way to understand how this works is to look at the source for `ReactCSSTransitionGroup`.