add css class for horizontal lists

app/templates/common/topnav.html

@@ -12,7 +12,7 @@
   {% else %}
     {% with user = get_active_user() %}
       Welcome, <a href="{{ url_for("users.page", username = user.username) }}">{{user.username}}</a>
-      <ul>
+      <ul class="horizontal">
         <li><a href="{{ url_for("users.settings", username = user.username) }}">Settings</a></li>
         <li><a href="{{ url_for("users.inbox", username = user.username) }}">Inbox</a></li>
         {% if config.DISABLE_SIGNUP and user.can_invite() %}