fix #1213 adding a class (#1229)

Author: giovapanasiti

app/views/feeds/new.html.erb

@@ -9,7 +9,7 @@
   <hr />
   <%= form_with(url: "/feeds", id: "add-feed-setup") do %>
     <div class="control-group">
-      <input name="feed_url" id="feed-url" type="text" value="<%= @feed_url %>" autofocus/>
+      <input name="feed_url" class="form-control" id="feed-url" type="text" value="<%= @feed_url %>" autofocus/>
       <i class="icon-rss field-icon"></i>
       <label id="feed_url-label" class="field-label" for="feed_url"><%= t('feeds.add.fields.feed_url') %></label>
     </div>