Allow creating torrent files that are not relative to current working dir
Add tracker swarm test.

Doesn't work yet. (Leech and seeder don't connect to tracker.)
Improve logging.
Write out announce data correctly.
Log invalid announce URLs.
Use valid announce URL.
Compare source and leeched data to make sure they're equal.
Fix spelling.
Rechoke peers when peer interests change.
Shorten timeout because test runs more quickly.
Rename tests.bash testswarm.bash