title: How to implements a button tag to form_for helper?
body: <p>I need implements a helper that creates <code>&lt;button&gt;...&lt;/button&gt;</code> tag, I need to do some similar to this:</p>
  
  <pre><code>&lt;%= form_for(some_var) do |f| %&gt;
    &lt;%= f.submit '+' %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>The helper should work like this:</p>
  
  <pre><code>&lt;%= f.button '+' %&gt;
  # Returns
  &lt;button type="submit"&gt;+&lt;/button&gt;
  </code></pre>
  
  <p>I saw <a href="https://github.com/rails/rails/blob/master/actionpack/lib/action_view/helpers/form_tag_helper.rb#L458" rel="nofollow">https://github.com/rails/rails/blob/master/actionpack/lib/action_view/helpers/form_tag_helper.rb#L458</a> but this isn't implemented in Rails 3.0.7.</p>
  
  <p>What I need to do to implements this helper in my application?</p>