Fix link for Babel Stage 1

Author: twhitbeck

docs/api/createStore.md

@@ -46,7 +46,7 @@ console.log(store.getState())
 
 * It is up to you to choose the state format. You can use plain objects or something like [Immutable](http://facebook.github.io/immutable-js/). If you’re not sure, start with plain objects.
 
-* If your state is a plain object, make sure you never mutate it! For example, instead of returning something like `Object.assign(state, newData)` from your reducers, return `Object.assign({}, state, newData)`. This way you don’t override the previous `state`. You can also write `return { ...state, ...newData }` if you enable [ES7 object spread proposal](https://github.com/sebmarkbage/ecmascript-rest-spread) with [Babel stage 1](http://babeljs.io/docs/usage/experimental/).
+* If your state is a plain object, make sure you never mutate it! For example, instead of returning something like `Object.assign(state, newData)` from your reducers, return `Object.assign({}, state, newData)`. This way you don’t override the previous `state`. You can also write `return { ...state, ...newData }` if you enable [ES7 object spread proposal](https://github.com/sebmarkbage/ecmascript-rest-spread) with [Babel stage 1](https://babeljs.io/docs/plugins/preset-stage-1/).
 
 * For universal apps that run on the server, create a store instance with every request so that they are isolated. Dispatch a few data fetching actions to a store instance and wait for them to complete before rendering the app on the server.