Fixed test warning by using react-dom render

Author: bvaughn

src/Highlight.test.js

@@ -1,13 +1,13 @@
 import React from 'react'
-import { findDOMNode } from 'react-dom'
+import { findDOMNode, render } from 'react-dom'
 import expect from 'expect.js'
 import Highlight from './Highlight'
 
 describe('Highlight', () => {
   const language = 'javascript'
   const content = 'var foo = "Foo"; // comment'
   const node = document.createElement('div')
-  const highlight = React.render(
+  const highlight = render(
     <Highlight language={language}>
       {content}
     </Highlight>,