TODO

REFACTORING
* peer talks directly to piece picker
* peer connection manager (Swarm?)

OTHER STUFF
* Document TorrentManager class
* Torrent#on_complete callback
* PeerConnction -- reconnecting
* know if a peer is seeding or leeching and act accordingly (i.e. disconnect from a seeding peer if we're seeding too)
* command line client
  - expose files
* configuration file
* global choke algo!
* handle blocks at the torrent data level so we can download a piece from multiple peers
* sanity check peers
* break up/down rate out into own class
* handle last rate for rate measure?
* rename torrent_manager to torrent_client
* Sanity checking in protcol buffer
* TorrentTracker -- tracker_id
* TorrentTracker -- retry
* start/end game algo
* hashing w/o blocking
* web ui