title: Issue with URL string with special characters
body: <p>I downloaded a mp3 file from internet and then save it to document directory, now I tried to play it , but file has some characters like <code>Space</code> and <code>[]</code> ,and that makes app crash because it cannot locate the file. The original file name is like this :</p>
  
  <pre><code>Artist - Track [320].mp3
  </code></pre>
  
  <p>so the URL is :<code>http://sample.com/Artist%20-%20Track%20[320].mp3</code></p>
  
  <p>But my file downloader url string replace that standard url with this :</p>
  
  <pre><code>http://sample.com/Artist%20-%20Track%20%5D320%5D.mp3
  </code></pre>
  
  <p>As you can see the <code>[]</code> characters has been replaced with <code>%5D</code>!. What is the proper way to get url string ?</p>
  
  <p>Getting URL from UIWebView :</p>
  
  <pre><code>   func requestIsDownloadable( request: URLRequest) -&gt; Bool
      {
          let requestString : NSString = (request.url?.absoluteString)! as NSString
          let fileExtention : String = requestString.pathExtension.lowercased()
  
          fileTypes.fileTypeIcons(path: fileExtention as NSString , icon: fileType)
          fileName.text = requestString.lastPathComponent as String
  
      //******************************//
             fileURL.text = request.url?.absoluteString
  //******************************//
  
          let isDownloadable : Bool = (
              fileExtentions.contains(fileExtention)
          )
  
          return isDownloadable
      }
  
  
  
   func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebViewNavigationType) -&gt; Bool
      {
  
          if requestIsDownloadable(request: request)
          {
              initializeDownload(download: request)
              return false
          }
  
  
          //urlTextField.text = webView.request?.url?.absoluteString
  
          return true
      }
  </code></pre>