title: UITextView character limit count is incorrect with emoji
body: <p>I have an issue with my UITextView character limit where the count double, triple, or quadruple counts emoji. I want emoji to count as 1 character, the way they do in the Twitter iOS app. Here is the code I have in my <code>shouldChangeTextInRange</code> method</p>
  
  <pre><code>let characters = textView.text.characters.count + (text.characters.count - range.length)
          if characters &lt;= self.characterLimit {
              // update character limit label as we type
              self.characterLimitLabel.text = String(characters) + "/" + String(self.characterLimit)
              return true
          } else {
              return false
          }
  </code></pre>
  
  <p>What should I change to produce the proper result when accounting for emoji?</p>