Merge pull request facebook#482 from chenglou/data-lowercase

add docs lowercase mention for data- and aria-

docs/docs/ref-06-dom-differences.md

@@ -8,7 +8,7 @@ prev: events.html
 
 React has implemented a browser-independent events and DOM system for performance and cross-browser compatibility reasons. We took the opportunity to clean up a few rough edges in browser DOM implementations.
 
-* 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.
+* 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. **However**, `data-*` and `aria-*` attributes [conform to the specs](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes#data-*) and should be lower-cased only.
 * 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.
 * All event objects conform to the W3C spec, and all events (including submit) bubble correctly per the W3C spec. See [Event System](events.html) for more details.
 * The `onChange` event 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. See [Forms](forms.html) for more details.