Non-exhaustive list of changes:

Additions

Lavalink filters support.
Support Java's modified utf by including a dedicated utfm codec.
- This should provide fewer erroneous decodes, as well as displaying previously-unsupported characters.
Support Lavalink's new exception format (#105, contributors: @apex2504).
Utils.timestamp_to_mills helper function.
PlayerUpdateEvent.connected.
Custom source support + DeferredAudioTrack.
player.destroy.
Support for volume and pause kwargs in play().
@lavalink.listener decorator.
ssl support for nodes (wss/https).
/plugins route support (#124, contributors: @apex2504).
node_unavailable() method added to BasePlayer.
Docstrings.

user_id now accepts int or str.
HTTP-based functions now raise appropriate errors rather than returning false/misleading values.
Renamed lavalink.exceptions to lavalink.errors to be more inline with Error naming.
Websocket closures now have a default error messages.
Websocket closures now better attempts to extract the close code.
ConnectionResetError should be better handled.
Updated a few logging messages to better show which module emitted the log.
position and encoder_version properties are now exposed in decoded AudioTracks.
Documented player.channel_id.
player.guild_id is now an int.
TrackEndEvent.track is now marked Optional to cover any potential scenarios where track decoding fails.
Marked set_gain, set_gains, and reset_equalizer as deprecated.
- Their equivalents are listed in the docs, so endeavour to change this as they will probably be removed on the next minor/major version.
player.add parameter has been re-ordered to be more logical.
The behaviour of the requester param in player.add has been altered so that non-zero values now overwrite the track's requester.
get_tracks now returns a LoadResult class rather than the raw JSON (dict).
- Best effort was made to ensure this was backwards compatible, however it's marked as breaking as it's a large change, so you should verify you're unaffected.
AudioTrack supports construction from another AudioTrack instance.
Docstrings.

Lavalink.py client will no longer dispatch to empty hooks.
Altered how Lavalink's TrackStartEvent is processed internally to avoid emitting NoneType events.
Docstrings.

Any non-essential functions (basically routeplanner_* functions in Client) have been moved to Node. They didn't make sense as they required a Node instance, so it seemed more logical to incorporate them directly into the Node instance itself.
Refactored logging formats.