title: Form submitted twice, due to :remote=>true
body: <p>My form submitted twice, after double checked, it was cause by ':remote=>true'. I removed it, my project works well. Who can show me why? And how to use ':remote=>true'?</p>
  
  <p>My ruby code:</p>
  
  <pre><code>&lt;%= form_tag(admin_product_group_product_scopes_path(@product_group), :remote =&gt; true, :id =&gt; 'new_product_group_form') do %&gt;
      &lt;%
      options =
      grouped_options_for_select(
      Scopes::Product::SCOPES.map do |group_name, scopes|
        [
          t(:name, :scope =&gt; [:product_scopes, :groups, group_name]),
          scopes.keys.map do |scope_name|
            [ t(:name, :scope =&gt; [:product_scopes, :scopes, scope_name]), scope_name]
          end
        ]
      end
      )
      %&gt;
      &lt;p&gt;
        &lt;label for="product_scope_name"&gt;&lt;%= t('add_scope') %&gt;&lt;/label&gt;
        &lt;%= select_tag("product_scope[name]", options) %&gt;
        &lt;input type="submit" value="&lt;%= t('add') %&gt;" /&gt;
      &lt;/p&gt;
    &lt;% end %&gt;
  </code></pre>
  
  <p>The final html code in browser.</p>
  
  <pre><code> &lt;form accept-charset="UTF-8" action="/admin/product_groups/17/product_scopes" data-remote="true" id="new_product_group_form" method="post"&gt;&lt;div style="margin:0;padding:0;display:inline"&gt;&lt;input name="utf8" type="hidden" value="✓"&gt;&lt;input name="authenticity_token" type="hidden" value="GocX/l4ZNgF/feKtzC8FuohebM2k5MuIHtdeGp2Oi0A="&gt;&lt;/div&gt;
      &lt;p&gt;
        &lt;label for="product_scope_name"&gt;Add a scope&lt;/label&gt;
        &lt;select id="product_scope_name" name="product_scope[name]"&gt;&lt;optgroup label="Taxon"&gt;&lt;option value="taxons_name_eq"&gt;In Taxon(without descendants)&lt;/option&gt;
  &lt;option value="in_taxons"&gt;In taxons and all their descendants&lt;/option&gt;&lt;/optgroup&gt;&lt;optgroup label="Text search"&gt;&lt;option value="in_name"&gt;Product name have following&lt;/option&gt;
  &lt;option value="in_name_or_keywords"&gt;Product name or meta keywords have following&lt;/option&gt;
  &lt;option value="in_name_or_description"&gt;Product name or description have following&lt;/option&gt;
  &lt;option value="with_ids"&gt;Products with IDs&lt;/option&gt;&lt;/optgroup&gt;&lt;optgroup label="Values"&gt;&lt;option value="with"&gt;With value&lt;/option&gt;
  &lt;option value="with_property"&gt;With property&lt;/option&gt;
  &lt;option value="with_property_value"&gt;With property value&lt;/option&gt;
  &lt;option value="with_option"&gt;With option&lt;/option&gt;
  &lt;option value="with_option_value"&gt;With option and value&lt;/option&gt;&lt;/optgroup&gt;&lt;optgroup label="Price"&gt;&lt;option value="price_between"&gt;Price between&lt;/option&gt;
  &lt;option value="master_price_lte"&gt;Master price lesser or equal to&lt;/option&gt;
  &lt;option value="master_price_gte"&gt;Master price greater or equal to&lt;/option&gt;&lt;/optgroup&gt;&lt;/select&gt;
        &lt;input type="submit" value="Add"&gt;
      &lt;/p&gt;
  &lt;/form&gt;
  </code></pre>