Merge pull request #52 from nictuku/master

Fix crash when using DHT.
Implement choker policy.

Not hooked up yet, but we have tests. :-)
Merge branch 'master' of github.com:jackpal/Taipei-Torrent
Implement classic BitTorrent choking policy.

...no anti-snubbing.
Calculate percent complete.
Update TODO
Update some todos.
Add --seedRatio flag

Torrents automatically quit seeding when the seedRatio is achieved.

By default is +Inf, so never quits seeding. (Same as before.)

Updated test script to quit immediately.
Update TODO