Finished draft of BEncoding library, integrated with cabal.

Added:
  -.gitignore
  -Setup.hs and overflow.cabal.
Modified
  -overflow.hs
    -Has basic tests for BEncoding.
  -src/BEncode.hs
    -Added decode function, which is left as a debugging mechanism for now.
    -Added functions which parse the full BEncoding specification.  Some are not complete and need to take edge cases into account.