Very basic torrent client as a way to learn Racket.

• Announcing/Peer requesting:
  • Throught UDP trackers (only HTTP right now).
  • Use Magnet URIs in addition to torrent files.
• Upload to peers.
• Consider multiple trackers.
• Proper exception handling.
• Proper logging (the current output is basically pure noise)
• Unreinvent all the wheels as I learn how to write idiomatic Racket.
• More test (only a very small subset of function is covered).