Merge pull request #19 from asapach/master

support `destroy` callback
0.6.0
bumping peer-wire-swarm
0.6.1
Update dependency on bittorrent-tracker

Fixes handling big files
https://github.com/feross/bittorrent-tracker/issues/11
Merge pull request #21 from thermatk/patch-1

Update dependency on bittorrent-tracker
synched the fork