Update blog post react-test-renderer import (jestjs#1337)

Official package implemented in facebook/react#7362

blog/2016-07-27-jest-14.md

@@ -14,7 +14,7 @@ One of the big open questions was how to write React tests efficiently. There ar
 Together with the React team we created a new test renderer for React and added snapshot testing to Jest. Consider this [example test](https://github.com/facebook/jest/blob/master/examples/snapshot/__tests__/Link.react-test.js) for a simple [Link component](https://github.com/facebook/jest/blob/master/examples/snapshot/Link.react.js):
 
 ```javascript
-import renderer from 'react/lib/ReactTestRenderer';
+import renderer from 'react-test-renderer';
 test('Link renders correctly', () => {
   const tree = renderer.create(
     <Link page="http://www.facebook.com">Facebook</Link>