title: Rails simple_form attribute required mark (*)
body: <p>I am using Simple Form in my app and I'd like to remove the <code>*</code> to indicate an attribute is required on all of my forms (existing and those yet to be created).  </p>
  
  <p>I have tried to set in <code>simple_form.rb</code>:</p>
  
  <pre><code>  # Whether attributes are required by default (or not). Default is true.
    config.required_by_default = false
  </code></pre>
  
  <p>And I've tried to modify <code>simple_form.en.yml</code>:</p>
  
  <pre><code>   required:
        text: 'required'
        mark: ''  # &lt;------ tried setting this to blank.
  </code></pre>
  
  <p>I know I can set <code>:required =&gt; false</code> on each field, but I want to clean up the views &amp; set it once.</p>