fix code style for ES6 classes

Author: ara4n

code_style.md

@@ -149,7 +149,7 @@ ECMAScript
 
 React
 -----
-- Use ES6 classes, although bear in mind a lot of code uses createClass.
+- Use React.createClass rather than ES6 classes for components, as the boilerplate is way too heavy on ES6 currently.  ES7 might improve it.
 - Pull out functions in props to the class, generally as specific event handlers:
 
   ```jsx