Hide group dashboard and project sidebar for xs size

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/groups/show.html.haml

 .dashboard
-  .activities.col-md-8.hidden-sm
+  .activities.col-md-8.hidden-sm.hidden-xs
     - if current_user
       = render "events/event_last_push", event: @last_push
       = link_to dashboard_path, class: 'btn btn-tiny' do

app/views/projects/show.html.haml

@@ -6,7 +6,7 @@
     = render 'shared/event_filter'
     .content_list
     = spinner
-  .col-md-3.project-side.hidden-sm
+  .col-md-3.project-side.hidden-sm.hidden-xs
     .clearfix
       - if @project.archived?
         .alert.alert-warning