Add deprecation note to blog post and changelog

_posts/2015-03-10-react-v0.13.md

@@ -35,6 +35,7 @@ We've also published version `0.13.0` of the `react` and `react-tools` packages
 
 #### Breaking Changes
 
+* Deprecated patterns that warned in 0.12 no longer work: most prominently, calling component classes without using JSX or React.createElement and using non-component functions with JSX or createElement
 * Mutating `props` after an element is created is deprecated and will cause warnings in development mode; future versions of React will incorporate performance optimizations assuming that props aren't mutated
 * Static methods (defined in `statics`) are no longer autobound to the component class
 * `ref` resolution order has changed slightly such that a ref to a component is available immediately after its `componentDidMount` method is called; this change should be observable only if your component calls a parent component's callback within your `componentDidMount`, which is an anti-pattern and should be avoided regardless