Update DOM differences docs to include a note about the style attribute.

docs/09-reference.md

@@ -205,4 +205,5 @@ React has implemented a browser-independent events and DOM system for performanc
 * All events (including submit) bubble correctly per the W3C spec
 * All event objects conform to the W3C spec
 * All DOM properties and attributes (including event handlers) should be camelCased to be consistent with standard JavaScript style. We intentionally break with the spec here, since the spec is inconsistent.
+* The `style` attribute accepts a JavaScript object with camelCased properties rather than a CSS string. This is consistent with the DOM `style` JavaScript property, is more efficient, and prevents XSS security holes.
 * `onChange` behaves as you would expect it to: whenever a form field is changed this event is fired rather than inconsistently on blur. We intentionally break from existing browser behavior because `onChange` is a misnomer for its behavior and React relies on this event to react to user input in real time.