title: How to set minimum and maximum number of tags?
body: <p>I am using <code>acts-as-taggable-on</code> gem and I am trying to make some sort of the validation on number of tags. I followed this tutorial and it works fine: <a href="http://railscasts.com/episodes/382-tagging" rel="nofollow">http://railscasts.com/episodes/382-tagging</a></p>
  
  <p>I have an article which acts as taggable. For now I validate that tags need to be present and number of characters:</p>
  
  <pre><code>class Article &lt; ActiveRecord::Base
    acts_as_taggable
    validates :tag_list, presence: true, length: { maximum: 100 }
  end
  </code></pre>
  
  <p>This is not really good solution for tags as there are many of them with many different sizes and they are separated by commas. How can I set required minimum and maximum number of tags which need to be connected with article? I would like to set minimum to 3 tags and maximum to 10 tags so length of text is not a good solution.</p>
  
  <p>Thank you for your help :)</p>