<div class="sidebar-container col-md-3">
  <ul class="sidebar-content">
    <li class="collapsed active" data-toggle="collapse" data-target="#search-field">
      <a href="#">Search</a>
    </li>
    <ul id="search-field" class="sub-menu collapse">
      <li>
        <div class="input-group">
          <input type="text" class="form-control" id="search_box" autocomplete="off" placeholder="Search for..." />
          <span class="input-group-btn">
            <button class="btn btn-default" type="button">Go!</button>
          </span>
        </div>
      </li>
    </ul>
    {% if site.categories %}
    <li class="collapsed active" data-toggle="collapse" data-target="#categories">
      <a href="#">Categories</a>
    </li>
    <ul id="categories" class="sub-menu collapse">
      {% for category in site.categories %}
      <li><a href="#">{{ category | first }}</a></li>
      {% endfor %}
    </ul>
    {% endif %}
  </ul>
</div><!-- .sidebar-container -->

<div class="sidebar-container col-md-3">
  <ul class="sidebar-content">
    <li class="collapsed active" data-toggle="collapse" data-target="#search-field">
      <a href="#">Search</a>
    </li>
    <ul id="search-field" class="sub-menu collapse">
      <li>
        <div id="search" class="input-group">
          <form action="/sidebar" method="get">
            <input type="text" id="search-query" name="q" placeholder="Enter a keyword..." class="form-control" autocomplete="off" />
          </form>
        </div>
        <section id="search-results" style="display: none;">
          <p>Search Results:</p>
          <div class="entries"></div>
        </section>
      </li>
    </ul>
    {% if site.categories %}
    <li class="collapsed active" data-toggle="collapse" data-target="#categories">
      <a href="#">Categories</a>
    </li>
    <ul id="categories" class="sub-menu collapse">
      {% for category in site.categories %}
      <li><a href="#">{{ category | first }}</a></li>
      {% endfor %}
    </ul>
    {% endif %}
  </ul>
</div><!-- .sidebar-container -->

Add lunr styling to search field.
Add lunr styling to search field.
