tool to handle nested forms using jQuery

 Nested forms are forms that handle nested models and attributes in one form;
 e.g. a project with its tasks or an invoice with its line items.
 .
 Cocoon is an unobtrusive nested forms handling, using jQuery.
 It is form builder-agnostic, so it works with standard Rails, Formtastic,
 or SimpleForm. It is compatible with rails 3 and rails 4.