Almost finished with message logic.

peer.lua
  -Moved most logic variables into torrent.lua.  Peers now only keep track of their bitfield and a list of pending requests made to this peer.
request.lua
  -Object used to keep track of requests.
torrent.lua
  -Added several data structures to be used in higher-level logic:
    -missing: keeps track of which blocks we are missing.
    -rarity: rates pieces based on how rare they are.
    -uploadQueue: a pipeline of requests we need to upload to peers.
    -downloadQueue: a pipeline of requests we need to ask peers to upload to us.
    -unchokeQueue: keeps track of and orders which peers we should unchoke.
    -interestedQueue: keeps track of and orders which peers we should become interested in.
    -content: a cache of the actual block data.
  -Added high-level logic to messageHandler for all message ids.