title: simple_form error messages do not go away
body: <p>I'm using simple_form with twitter bootstrap on Rails.</p>
  
  <p>Everything works great, except when showing live validations in a form-inline class.  My code for the form is:</p>
  
  <pre><code>&lt;%= simple_form_for @message, 
                      url: mailing_list_path,
                      html: { class: "form-inline" },
                      method: :post,
                      validate: true do |f| %&gt;
  
      &lt;%= f.input_field :email_address, label: false %&gt;
      &lt;%= f.submit "Submit" %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>This shows the error message properly (e.g. "is invalid"), but if I click off the input and then back on again, it adds another message (e.g. it would say "is invalid is invalid"). For example, two sequential invalid entries and then a blank entry would give:</p>
  
  <p><img src="https://i.stack.imgur.com/8B8V6.png" alt="errors are not removed"></p>
  
  <p>Is there any way to have simple_form remove the existing error message before adding a new one?</p>