title: Make button overlap div
body: <p>I'm trying to create a button which overlaps a div. Ideally, I want the button to always appear at the bottom, center of the div even when resized. How can I go about this? Normally I can create overlapping div's when they're not needed, but when I need one, they don't work!</p>
  <p>I have the following markup:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.call_to_action{
    background-color: #000;
    height: 300px;
  }
  .button {
      background: #c43d3d;
      font-size: 24px;
      color: #FFFFFF;
      margin: 0;
      padding: 0;
      border: 0;
      cursor: pointer;
      padding: 20px 25px;
      width:200px;
      text-align: center;
  }
  .overlap-header {
      position: relative;
  }
  .overlap-button {
      position: relative;
      display: block;
      margin: 100px auto 25px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;section class="call_to_action"&gt;
    &lt;div class="wrapper"&gt;
      &lt;div class="content-block"&gt;
        &lt;div class="content-block-wrapper"&gt;
          &lt;div class="overlap-header"&gt;
            &lt;span class="button overlap-button"&gt;Read more&lt;/span&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/section&gt;</code></pre>
  </div>
  </div>
  </p>
  <p><a href="https://i.stack.imgur.com/utbG2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/utbG2.png" alt="enter image description here" /></a></p>
  <p>Here's an image of what I'm trying to achieve.</p>