### Added

- `client.listening` property to signal whether TCP server is listening
for incoming
  connections.

### Changed

- Merged `Swarm` class into `Torrent` object. Properties on
`torrent.swarm` (like
  `torrent.swarm.wires`) now exist on `torrent` (e.g. `torrent.wires`).

- `torrent.addPeer` can no longer be called before the `infoHash` event
has been
  emitted.

- Remove `torrent.on('listening')` event. Use `client.on('listening')`
instead.

- Remove support from `TCPPool` for listening on multiple ports. This
was not used by
  WebTorrent and just added complexity. There is now a single `TCPPool`
instance for the
  whole WebTorrent client.

- Deprecate: Do not use `client.download()` anymore. Use `client.add()`
instead.

- Deprecate: Do not use `torrent.swarm` anymore. Use `torrent` instead.

### Fixed

- When there is a `torrent.on('error')` listener, don't also emit
  `client.on('error')`.

- Do not return existing torrent object when duplicate torrent is
added. Fire an
  `'error'` event instead.

- Memory leak of `Torrent` object caused by `RarityMap`

- Memory leak of `Torrent` object caused by `TCPPool`

- `client.ratio` and `torrent.ratio` are now calculated as `uploaded /
received` instead
  of `uploaded / downloaded`.

- Only pass `torrent.infoHash` to the Chunk Store constructor, instead
of the `Torrent`
  instance itself, to prevent accidental memory leaks of the `Torrent`
object by the
  store. (Open an issue if you were using other properties. They can be
re-added.)

- Non-fatal errors with a single torrent will be emitted at
`torrent.on('error')`. You
  should listen to this event. Previously, all torrent errors were also
emitted on
  `client.on('error')` and handling `torrent.on('error')` was optional.
This design is
  better since now it is possible to distinguish between fatal client
errors
  (`client.on('error')`) when the whole client becomes unusable versus
recoverable errors
  where only a single torrent fails (`torrent.on('error')`) but the
client can continue to
  be used. However, if there is no `torrent.on('error')` event, then
the error will be
  forwarded to `client.on('error')`. This prevents crashing the client
when the user
  only has a listener on the client, but it makes it impossible for
them to determine
  a client error versus a torrent error.

- Errors creating a torrent with `client.seed` are now emitted on the
returned `torrent`
  object instead of the client (unless there is no event listeners on
  `torrent.on('error')` as previously discussed). The torrent object is
now also destroyed
  automatically for the user, as was probably expected.

- If `client.get` is passed a `Torrent` instance, it now only returns
it if it is present
  in the client.