title: MUI dark theme isn't applied to the background
body: <p>I have my react application where I want to apply MUI <code>darkBaseTheme</code>. Without it, part of my app looks like this:</p>
  <p><a href="https://i.stack.imgur.com/yHRd2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/yHRd2.png" alt="enter image description here" /></a></p>
  <p>After I wrap all the html stuff in my <code>render()</code> with:</p>
  <pre><code>&lt;MuiThemeProvider muiTheme={getMuiTheme(darkBaseTheme)}&gt;
  &lt;/MuiThemeProvider&gt;
  </code></pre>
  <p>Having those imports:</p>
  <pre><code>import MuiThemeProvider from 'material-ui/styles/MuiThemeProvider'; // add
  import RaisedButton from 'material-ui/RaisedButton'; // add
  import getMuiTheme from 'material-ui/styles/getMuiTheme';
  import darkBaseTheme from 'material-ui/styles/baseThemes/darkBaseTheme';
  </code></pre>
  <p>It looks like this:</p>
  <p><a href="https://i.stack.imgur.com/i8RkD.png" rel="noreferrer"><img src="https://i.stack.imgur.com/i8RkD.png" alt="enter image description here" /></a></p>
  <p>So it changed <code>RaisedButtons</code>. I know it shouldn't change html ones. But why didn't it change the background to dark? Is there a way to do this, or do I have to do it manually without MUI?</p>