Dont render more than 20 group members on Project#members page

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

app/views/projects/team_members/_group_members.html.haml

+- group_users_count = @group.users_groups.count
 .ui-box
   .title
     %strong #{@group.name}
-    group members (#{@group.users_groups.count})
+    group members (#{group_users_count})
     .pull-right
       = link_to members_group_path(@group), class: 'btn btn-small' do
         %i.icon-edit
   %ul.well-list
-    - @group.users_groups.order('group_access DESC').each do |member|
+    - @group.users_groups.order('group_access DESC').limit(20).each do |member|
       = render 'users_groups/users_group', member: member, show_controls: false
+    - if group_users_count > 20
+      %li
+        and #{group_users_count - 20} more. For full list visit #{link_to 'group members page', members_group_path(@group)}