title: On edit, use selected in select form helper
body: <p>I've got a select in my form with all the groups. So I loop through all available groups.</p>
  
  <p>However; When I try to edit a client, the selectbox doesn't add a selected to the group i've selected. Most likely because of the loop in it. How can I make the right one selected?</p>
  
  <p><code>&lt;%= f.select(:group_id, options_for_select(@usersGroups.collect{ |u| [u.name, u.id] }), :prompt =&gt; "Kies een groep") %&gt;</code></p>