title: Babel polyfill with webpack
body: <p>Do I need to include <code>import "babel-polyfill"</code> to the top of each entry file, or is it enough to have <code>babel-polyfill</code> rule just in webpack.config file? I am confused by polyfill docs and still getting following error: <code>only one instance of babel-polyfill is allowed</code></p>
  
  <p>My webpack.config in short:</p>
  
  <pre><code>  entry1: ['babel-polyfill', 'homepage.js'],
    entry2: ['babel-polyfill', 'not-homepage.js'],
    entry3: ['babel-polyfill', 'contacts.js']
  </code></pre>