title: Simple_form: how to change input's wrapper's class?(not the wrapper_html effect on)
body: <p>I have a problem when using simple_form and Bootstrap 3. About the input's wrapper tag. Show codes below:</p>
  
  <p><strong>view code</strong>(with haml)</p>
  
  <pre><code>= simple_form_for @refer_email_form, url: create_refer_message_path, html: { class: "form-horizontal" } do |f|
    = f.input :to, label_html: { class: "col-sm-2" }
    = f.input :subject, label_html: { class: "col-sm-2" }
  </code></pre>
  
  <p><strong>config/simple_form_bootstrap.rb</strong></p>
  
  <pre><code>SimpleForm.setup do |config|
    config.input_class = "form-control"
  
    config.wrappers :bootstrap, tag: 'div', class: 'form-group', error_class: 'error' do |b|
      b.use :html5
      b.use :placeholder
      b.use :label, class: "control-label"
      # b.wrapper tag: 'div', class: "col-sm-6" do |ba|
      b.wrapper tag: 'div' do |ba|
        ba.use :input
        ba.use :error, wrap_with: { tag: 'span', class: 'help-inline' }
        ba.use :hint,  wrap_with: { tag: 'p', class: 'help-block' }
      end
    end
  
   config.default_wrapper = :bootstrap
  </code></pre>
  
  <p>I just want to use the "Horizontal form" by default</p>
  
  <p><strong>the generated html</strong></p>
  
  <pre><code>...
  \&lt;div class="form-group string optional refer_email_form_to"&gt;
    &lt;label class="string optional control-label col-sm-2" for="refer_email_form_to"&gt;To&lt;/label&gt;
    &lt;div&gt;
      &lt;input class="string optional form-control" id="refer_email_form_to"   name="refer_email_form[to]" type="text"&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  ...
  </code></pre>
  
  <p>What I want is to change the <code>&lt;div&gt;</code>'s class which just wrap the <code>&lt;input&gt;</code> element, something like this:</p>
  
  <pre><code>...
  &lt;div class="col-sm-6"&gt;
    &lt;input class="string optional form-control" id="refer_email_form_to"   name="refer_email_form[to]" type="text"&gt;
  &lt;div&gt;
  ...
  </code></pre>
  
  <p>I've read the README from simple_form's github page, and googled for this problem, I know I can achieve this by adding <code>b.wrapper tag: 'div', class: "col-sm-6" do |ba|</code> to the <strong>config/simple_form_bootstrap.rb</strong> file, but the real problem is that I may use different class for the div, maybe <code>col-sm-9</code> in other form. And I tried the <code>input_html</code>, <code>wrapper_html</code> in the view, but the <code>wrapper_html</code> effects on the first <code>&lt;div class="form-group"&gt;</code>, and <code>input_html</code> only effects on the <code>&lt;input&gt;</code> element</p>
  
  <p>Is there any way to change the <code>&lt;input&gt;</code>'s wrapper <code>&lt;div&gt;</code> dynamically in the view ?</p>