title: Showing fields with errors for nested forms in Rails 3.2 + SimpleForm
body: <p>I have a <code>Flight</code> model nested inside a <code>FlightLog</code> model. A <code>FlightLog</code> may contain many flights.</p>
  
  <p>I'm using SimpleForm with the bootstrap installation, which makes it possible to surround form elements with errors with the error class when a validation fails.</p>
  
  <p>The problem is, that even though validations are triggered for the nested model, <em>the fields with errors inside the simple_fields_for are not being marked</em>, so it's not possible to determine which attribute is not valid.</p>
  
  <p>After examining the errors hash when calling the create action, I can see that it is correctly populated with the errors at the top level, and the errors of the nested resources inside each resource.</p>
  
  <p>How could I modify the behavior of simple_form to add the errors class to the control group of each nested model to match the behavior of the parent?</p>
  
  <p>Thanks in advance.</p>
  
  <p><img src="https://i.stack.imgur.com/FDU7s.png" alt="enter image description here"></p>