Add Font Awesome Icons to all of our Buttons

说明：

Font Awesome 是一个非常方便的图标库。这些图片都是矢量图，以 .svg 文件格式保存。这些图标用起来就像字体一样。你可以使用像素单位来指定他们的大小，它们会继承父级HTML元素的字体大小。

使用 Font Awesome 分别为你的 info 按钮添加 info-circle 图标，为你的 delete 按钮添加 trash 图标。
你应该添加一个 <i class="fa fa-trash"></i> 到你的删除按钮元素中。
你应该添加一个 <i class="fa fa-info-circle"></i> 到你的 info 按钮元素中。
确保你的每一个 i 元素都有一个闭合标签，并且 <i class="fa fa-thumbs-up"></i> 在你的 like 按钮元素中。

原始代码：

<link href="//fonts.gdgdocs.org/css?family=Lobster" rel="stylesheet" type="text/css">
<style>
  h2 {
    font-family: Lobster, Monospace;
  }

  .thick-green-border {
    border-color: green;
    border-width: 10px;
    border-style: solid;
    border-radius: 50%;
  }
</style>

<div class="container-fluid">
  <div class="row">
    <div class="col-xs-8">
      <h2 class="text-primary text-center">CatPhotoApp</h2>
    </div>
    <div class="col-xs-4">
      <a href="#"><img class="img-responsive thick-green-border" src="/images/relaxing-cat.jpg"></a>
    </div>
  </div>
  <img src="/images/running-cat.jpg" class="img-responsive">
  <div class="row">
    <div class="col-xs-4">
      <button class="btn btn-block btn-primary"><i class="fa fa-thumbs-up"></i> Like</button>
    </div>
    <div class="col-xs-4">
      <button class="btn btn-block btn-info">Info</button>
    </div>
    <div class="col-xs-4">
      <button class="btn btn-block btn-danger">Delete</button>
    </div>
  </div>
  <p>Things cats <span class="text-danger">love:</span></p>
  <ul>
    <li>cat nip</li>
    <li>laser pointers</li>
    <li>lasagna</li>
  </ul>
  <p>Top 3 things cats hate:</p>
  <ol>
    <li>flea treatment</li>
    <li>thunder</li>
    <li>other cats</li>
  </ol>
  <form action="/submit-cat-photo">
    <label><input type="radio" name="indoor-outdoor"> Indoor</label>
    <label><input type="radio" name="indoor-outdoor"> Outdoor</label>
    <label><input type="checkbox" name="personality"> Loving</label>
    <label><input type="checkbox" name="personality"> Lazy</label>
    <label><input type="checkbox" name="personality"> Crazy</label>
    <input type="text" placeholder="cat photo URL" required>
    <button type="submit">Submit</button>
  </form>
</div>

调试代码：

<link href="//fonts.gdgdocs.org/css?family=Lobster" rel="stylesheet" type="text/css">
<style>
  h2 {
    font-family: Lobster, Monospace;
  }

  .thick-green-border {
    border-color: green;
    border-width: 10px;
    border-style: solid;
    border-radius: 50%;
  }
</style>

<div class="container-fluid">
  <div class="row">
    <div class="col-xs-8">
      <h2 class="text-primary text-center">CatPhotoApp</h2>
    </div>
    <div class="col-xs-4">
      <a href="#"><img class="img-responsive thick-green-border" src="/images/relaxing-cat.jpg"></a>
    </div>
  </div>
  <img src="/images/running-cat.jpg" class="img-responsive">
  <div class="row">
    <div class="col-xs-4">
      <button class="btn btn-block btn-primary"><i class="fa fa-thumbs-up"></i> Like</button>
     </div>
    <div class="col-xs-4">
      <button class="btn btn-block btn-info"><i class="fa fa-info-circle"></i>Info</button>
    </div>
    <div class="col-xs-4">
      <button class="btn btn-block btn-danger"><i class="fa fa-trash"></i>Delete</button>
    </div>
  </div>
  <p>Things cats <span class="text-danger">love:</span></p>
  <ul>
    <li>cat nip</li>
    <li>laser pointers</li>
    <li>lasagna</li>
  </ul>
  <p>Top 3 things cats hate:</p>
  <ol>
    <li>flea treatment</li>
    <li>thunder</li>
    <li>other cats</li>
  </ol>
  <form action="/submit-cat-photo">
    <label><input type="radio" name="indoor-outdoor"> Indoor</label>
    <label><input type="radio" name="indoor-outdoor"> Outdoor</label>
    <label><input type="checkbox" name="personality"> Loving</label>
    <label><input type="checkbox" name="personality"> Lazy</label>
    <label><input type="checkbox" name="personality"> Crazy</label>
    <input type="text" placeholder="cat photo URL" required>
    <button type="submit">Submit</button>
  </form>
</div>