title: Rails acts-as-taggable-on with select2 (and simple_form)
body: <p>I would like to have a select2 dropdown of tags, where i could select multiple existing tags and add new ones.</p>
  
  <p>I have tried many different ways and i either don't get select2 box working or only one value is passed (last one).</p>
  
  <p>This is closest i got (passes last value):</p>
  
  <pre><code>&lt;%= f.input :tag_list, collection: @model.tags.map { |t| t.name }, input_html: { :style=&gt; 'width: 300px', class: "taggable", data: { placeholder: "Tags" }} %&gt;
  </code></pre>