anchor.diff:        <a href="#" data-activates="mobile-demo" class="button-collapse"><i class="material-icons">menu</i></a>
         <ul class="right hide-on-med-and-down">
           <% if current_user %>
  +          <li><a href="/logout">Logout</a></li>
           <% else %>
             <li><a href="/login">Login</a></li>
             <li><a href="/users/new">Sign Up</a></li>
  
positive.code:       </ul>
        <ul class="side-nav" id="mobile-demo">
          <% if current_user %>
          <% else %>
            <li><a href="/login">Login</a></li>
            <li><a href="/users/new">Sign Up</a></li>
  
negative.code:   </nav>
  
    <% if current_user %>
      <%= image_tag current_user.avatar.url(:thumb) %> | <%= current_user.name %>
    <% end %>
  
  <%= yield %>
  