title: Dialog skinning with AppCompat-v7 22 results in ugly shadows on api < 21
body: <p>I'm using AppCompat to write a material design styled app. Since AppCompat does not affect dialogs, I'm skinning the dialogs as such:</p>
  
  <p>styles.xml:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;style name="AppTheme.Base" parent="Theme.AppCompat"&gt;
      &lt;!-- Set AppCompat’s color theming attrs --&gt;
      &lt;item name="colorPrimary"&gt;@color/green&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/green_darker&lt;/item&gt;
      &lt;item name="colorAccent"&gt;@color/accent&lt;/item&gt;
  
      &lt;item name="android:alertDialogTheme"&gt;@style/alertDialog&lt;/item&gt;
      &lt;item name="android:dialogTheme"&gt;@style/alertDialog&lt;/item&gt;
  &lt;/style&gt;
  
  &lt;style name="alertDialog" parent="Theme.AppCompat.Dialog"&gt;
      &lt;item name="colorPrimary"&gt;@color/green&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/green_darker&lt;/item&gt;
      &lt;item name="colorAccent"&gt;@color/accent&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p></p>
  
  <p>I am gettings exactly what I wanted on android api >= 21, but on other devices I end up with a "box" around the dialogs.</p>
  
  <p>Is there a way to get rid of the "box" around the dialog and even get the colors and material theme applied on api &lt; 21, preferably without any additional depencendies?</p>
  
  <p>App on Api &lt; 21:</p>
  
  <p><img src="https://i.stack.imgur.com/4e2U2.png" alt="App on API &lt; 21"></p>
  
  <p>App on API >= 21:</p>
  
  <p><img src="https://i.stack.imgur.com/AAwfG.png" alt="App on API &gt;= 21"></p>