ab_test on button color

<% ab_test(:donate_color, "btn btn-primary btn-lg text-right", 
                          "btn btn-info btn-lg text-right", 
                          "btn btn-warning btn-lg text-right",
                          "btn btn-danger btn-lg text-right") do |color| %>
  <%= link_to 'Donate', donate_path, class: 'btn btn-danger btn-lg text-right' %>
<% end %>