title: Can' t resolve module - Material-UI
body: <p>I am getting error on trying to import a component from 'Material-Ui'. 
  Actually i am working with React and Webpack.
  I am wanna use "Card" component (<a href="http://www.material-ui.com/#/components/card" rel="nofollow noreferrer">http://www.material-ui.com/#/components/card</a>).</p>
  
  <p>Card import on my .js is like documentation -> </p>
  
  <pre><code>   import {Card} from 'material-ui/Card'
  </code></pre>
  
  <p>This is my Webpack log: </p>
  
  <blockquote>
    <p>Cannot resolve module 'react/lib/reactProdInvariant' in
    .../node_modules/material-ui/ReactFragment.</p>
  </blockquote>
  
  <p>Any idea?</p>