Add Babel version to blog post

_posts/2015-09-10-react-v0.14-rc1.md

@@ -111,7 +111,7 @@ These builds are also available in the `react` and `react-dom` packages on bower
 
 - #### Compiler optimizations
 
-    React now supports two compiler optimizations that can be enabled in Babel. Both of these transforms **should be enabled only in production** (e.g., just before minifying your code) because although they improve runtime performance, they make warning messages more cryptic and skip important checks that happen in development mode, including propTypes.
+    React now supports two compiler optimizations that can be enabled in Babel 5.8.23 and newer. Both of these transforms **should be enabled only in production** (e.g., just before minifying your code) because although they improve runtime performance, they make warning messages more cryptic and skip important checks that happen in development mode, including propTypes.
 
     **Inlining React elements:** The `optimisation.react.inlineElements` transform converts JSX elements to object literals like `{type: 'div', props: ...}` instead of calls to `React.createElement`.