title: Swift 4 'substring(from:)' is deprecated: Please use String slicing subscript with a 'partial range from' operator
body: <p>i've just converted my little app but i've found this error:
  'substring(from:)' is deprecated: Please use String slicing subscript with a 'partial range from' operator</p>
  
  <p>my code is:</p>
  
  <pre><code>    let dateObj = dateFormatterFrom.date(from: dateStringa)
  
  
      if dateObj != nil {
          cell.detailTextLabel?.text = dateFormatterTo.string(from:(dateObj!))
      } else {
          let index = thisRecord.pubDate.index(thisRecord.pubDate.startIndex, offsetBy: 5)
          cell.detailTextLabel?.text = thisRecord.pubDate.substring(from: index)
      }
  </code></pre>