torrent-create and torrent-verify did not work correctly when a single
file is present in metainfo torrent file. torrent-create now fails if
the path passed as an argument does not exist. I've als modified
dht.go which now handles the case when an empty string is passed in
DHT bootstrap nodes slice. Finally in span.go I've sneaked in cheekily
a change which defines a type more like idiomatic Go (I have an OCD :-))
Piece state is broken up into several dimensions.
Implement keep-alive in connection writer.
Lazily hash pieces, only as requested.
Replace client actor mechanism with a mutex.
Fix runConnection/connectionLoop/handshake misnomers.
Fix broken reading from partially complete pieces.
Milos Gajdos