* Properly encapsulate the mmap/span stuff.
 * Finish balancing socketsPerTorrent and half-open, handshakes and worst conns.
 * Use big.Int, and it's Xor(), and SetBytes() functions for DHT node ID distances.
 * Add a coarse-responsive download strategy, that prioritizes pieces instead of chunks.
 * Track upload and download data.
 * Emulate a UDP server in the UDP tracker tests.
 * Ping nodes that stop being good.
 * Cache completed torrent files from magnet.
 * Don't download the last piece preemptively because it appears partial.
 * Make use of sparse file regions in download data for faster hashing.
 * Add an alternative to mmap()'ed torrent data.
 * Implement block lists.