title: Property 'theme' does not exist when using typescript
body: <p>I am creating a ReactJS starter project using typescript with material-ui v1.x beta.</p>
  
  <p>The themes as explained at: <a href="https://material-ui-1dab0.firebaseapp.com/customization/themes/" rel="noreferrer">https://material-ui-1dab0.firebaseapp.com/customization/themes/</a>
  do not work. Typescript complains about the property 'theme' not existing. I have been fiddling with the index.d.ts in @types/material-ui replacing the interface 'muiTheme' to 'theme' which results in a whole lot of other errors.</p>
  
  <p>When using 'muiTheme' property instead the errors are gone, however only the default colours are used indicating my custom theme is not used at all.</p>
  
  <p>My code:</p>
  
  <pre><code>import * as React from 'react';
  import { MuiThemeProvider } from 'material-ui/styles';
  import createMuiTheme from 'material-ui/styles/theme';
  import createPalette from 'material-ui/styles/palette';
  import { teal, bluegrey, red } from 'material-ui/colors';
  import Button from 'material-ui/Button';
  
  const theme: any = createMuiTheme({
    palette: createPalette({
      primary: teal, // Purple and green play nicely together.
      accent: {
        ...bluegrey,
        A400: '#00e677',
      },
      error: red,
    }),
  });
  
  function Palette() {
    return (
      &lt;MuiThemeProvider theme={theme}&gt;
        &lt;div&gt;
          &lt;Button color="primary"&gt;
            {'Primary'}
          &lt;/Button&gt;
          &lt;Button color="accent"&gt;
            {'Accent'}
          &lt;/Button&gt;
        &lt;/div&gt;
      &lt;/MuiThemeProvider&gt;
    );
  }
  </code></pre>
  
  <p>Typescript:</p>
  
  <pre><code>(21,23): error TS2339: Property 'theme' does not exist on type 'IntrinsicAttributes &amp; IntrinsicClassAttributes&lt;MuiThemeProvider&gt; &amp; Readonly&lt;{ children?: ReactNod...'.
  </code></pre>