/favorites: replace favorites view with ordfav: search.

Make /favorites redirect to a ordfav:<user> search instead of having a
separate view just for favorites. This duplicated a lot of code for no
good reason.

app/views/users/_post_summary.html.erb

@@ -14,7 +14,7 @@
 <% if presenter.has_favorites? %>
   <div class="box user-favorites">
     <h2>
-      <%= link_to "Favorites", favorites_path(:user_id => user.id) %>
+      <%= link_to "Favorites", posts_path(tags: "ordfav:#{user.name}") %>
     </h2>
     <div>
       <% presenter.favorites.each do |post| %>
@@ -39,4 +39,4 @@
       </div>
     </div>
   <% end %>
-<% end %>
+<% end %>