Remove order_selector partial

Most of the logic was pulled out into DebatesHelper so having
the partial no longer makes sense.

app/views/debates/_order_selector.erb

@@ -1,5 +0,0 @@
-<form class="inline-block">
-   <select class="js-order-selector" name="order-selector"> 
-     <%= available_options_for_order_selector(@valid_orders, @order) %>
-   </select>
-</form>

app/views/debates/index.html.erb

@@ -4,7 +4,11 @@
   <div class="filters row">
     <div class="small-12 column">
       <h2><%= t("debates.index.showing") %></h2>
-      <%= render 'order_selector' %>
+      <form class="inline-block">
+         <select class="js-order-selector" name="order-selector"> 
+           <%= available_options_for_order_selector(@valid_orders, @order) %>
+         </select>
+      </form>
     </div>
   </div>
   <!-- /. Filters -->