Add Drive Virtual to the list of Sync Tools

non-free.md

@@ -23,6 +23,7 @@
 ## File Sharing and Synchronization
 
   * [Bittorrent Sync](https://www.getsync.com/) `⊘ Proprietary` - BitTorrent Sync by BitTorrent, Inc is a proprietary peer-to-peer file synchronisation tool.
+  * [Drive Virtual](http://www.drivevirtual.com/) `⊘ Proprietary` - With Drive Virtual you can sync, backup and share your files privately with your own FTP (SFTP) server or account.
 
 ## Media Streaming