<nav role="navigation" class="user-navigation">
  <ul>
    <!-- always -->
    <li class="user-navigation--search">
      <!-- <svg viewBox="0 0 32 32"><use xlink:href="#search1"></use></svg> -->
      <%= render 'thredded/search/form' %>
    </li>

    <!-- if logged in -->
    <li class="">
      <a href="#">
        <!-- <svg viewBox="0 0 32 32"><use xlink:href="#user1"></use></svg> -->
        <span>Sign In / Register</span>
      </a>
    </li>

    <!-- if not logged in -->
    <!-- <li class="main&#45;nav&#45;notification&#45;preferences"> -->
    <!--   <a href="#"> -->
    <!--     <!&#45;&#45; <svg viewBox="0 0 32 32"><use xlink:href="#bell"></use></svg> &#45;&#45;> -->
    <!--     <span>Notification Settings</span> -->
    <!--   </a> -->
    <!-- </li> -->
    <!--  -->
    <!-- <li class="main&#45;nav&#45;notification&#45;preferences"> -->
    <!--   <a href="#"> -->
    <!--     <!&#45;&#45; <svg viewBox="0 0 32 32"><use xlink:href="#bell"></use></svg> &#45;&#45;> -->
    <!--     <span>UserName</span> -->
    <!--   </a> -->
    <!-- </li> -->
  </ul>
</nav>

<nav role="navigation" class="user-navigation">
  <ul>
    <li class="user-navigation--search">
      <%= render 'thredded/search/form' %>
    </li>

    <% if signed_in? %>
      <% if messageboard %>
        <li class="main--nav--notification--preferences">
          <%= link_to edit_messageboard_preferences_path(messageboard) do %>
            <span>Notification Settings</span>
          <% end %>
        </li>
      <% end %>

      <li class="main--nav--user">
        <%= link_to "/users/#{current_user}" do %>
          <span><%= current_user %></span>
        <% end %>
      </li>

      <li class="main--nav--sign-out">
        <%= link_to main_app.session_path, method: :delete do %>
         <span>Sign Out</span>
        <% end %>
      </li>

    <% else %>
      <li class="main--nav--sign-in-register">
        <%= link_to main_app.sessions_new_path do %>
          <span>Sign In / Register</span>
        <% end %>
      </li>
    <% end %>
  </ul>
</nav>

Clean up and flesh out top_nav partial
[JRO] Clean up and flesh out top_nav partial

Depending on whether users are signed in or not we will show the
appropriate links or items in the top nav.

* Remove unused SVG's.
* Addresses https://github.com/jayroh/thredded/issues/82
