1.4.0
General: Substantial API upgrades (see https://www.pettingzoo.ml/api), overhaul of the handling of agent death. In particular, the agents list now only contains live agents (agents which have not been done). Moved significant logic from wrappers to raw environment. Renamed max_frames to max_cycles and made the meaning of this argument consistent across all environments.
Atari: Fixed entombed_cooperative rewards, add support for custom ROM directory specification
Butterfly: Bug fixes in all environment, bumped PyGame and PyMunk versions
Classic: Bumped RLCard version, fixed default observation space for many environments depending on RLCard
SISL: Bug fixes in all environments
MAgent: Fixes to observation space of all environments
Bumped versions of all environments. There hopefully will be no more major API changes after this.