title: align-self: flex-end not moving item to bottom
body: <p>As you can see here: <a href="https://jsfiddle.net/0zq5a5xu/1/" rel="noreferrer">JSFiddle</a> </p>
  
  <p>I want author div to be at the bottom of his parent container. I tried with <code>align-self: flex-end;</code> but it's not working. What am I doing wrong?</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>.flexbox {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
  }
  
  .item {
    display: flex;
    flex-direction: column;
    width: 100px;
    border: 1px solid #000;
    padding: 10px;
  }
  
  .item .author {
    width: 100%;
    align-self: flex-end;
    border: 1px solid #000;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="flexbox"&gt;
  
    &lt;div class="item"&gt;
      &lt;div class="title"&gt;
        Title
      &lt;/div&gt;
      &lt;div class="content"&gt;
        Content
      &lt;/div&gt;
      &lt;div class="author"&gt;
        Author
      &lt;/div&gt;
    &lt;/div&gt;
  
    &lt;div class="item"&gt;
      &lt;div class="title"&gt;
        Title
      &lt;/div&gt;
      &lt;div class="content"&gt;
        Content&lt;br&gt;Content
      &lt;/div&gt;
      &lt;div class="author"&gt;
        Author
      &lt;/div&gt;
    &lt;/div&gt;
  
    &lt;div class="item"&gt;
      &lt;div class="title"&gt;
        Title
      &lt;/div&gt;
      &lt;div class="content"&gt;
        Content&lt;br&gt;Content&lt;br&gt;Content
      &lt;/div&gt;
      &lt;div class="author"&gt;
        Author
      &lt;/div&gt;
    &lt;/div&gt;
  
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>