Add page title to users statistics page

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

ee/app/views/admin/dashboard/stats.html.haml

-%h3 Users statistics
+- page_title 'Users statistics'
 
+%h3 Users statistics
 %table.table
   %tr
     %td Users total
     %td
       = User.count
+
   - if @admin_count
     %tr
       %td Admin users