Add white background to create MR banner

app/views/projects/_activity.html.haml

 - @no_container = true
 
-
 %div{ class: container_class }
   .nav-block.activity-filter-block
     - if current_user
       .controls
         = link_to namespace_project_path(@project.namespace, @project, format: :atom, private_token: current_user.private_token), title: "Feed", class: 'btn rss-btn' do
-          %i.fa.fa-rss
+          = icon('rss')
 
     = render 'shared/event_filter'
 

app/views/projects/_last_push.html.haml

 - if event = last_push_event
   - if show_last_push_widget?(event)
-    .row-content-block.top-block.clear-block.hidden-xs
+    .row-content-block.top-block.hidden-xs.white
       %div{ class: container_class }
         .event-last-push
           .event-last-push-text