Tensorboard support, refactored logger

Breaking Changes:

• Remove State-Dependent Exploration (SDE) support for TD3
• Methods were renamed in the logger:
  • logkv -> record, writekvs -> write, writeseq -> write_sequence,
  • logkvs -> record_dict, dumpkvs -> dump,
  • getkvs -> get_log_dict, logkv_mean -> record_mean,

New Features:

• Added env checker (Sync with Stable Baselines)
• Added VecCheckNan and VecVideoRecorder (Sync with Stable Baselines)
• Added determinism tests
• Added cmd_util and atari_wrappers
• Added support for MultiDiscrete and MultiBinary observation spaces (@rolandgvc)
• Added MultiCategorical and Bernoulli distributions for PPO/A2C (@rolandgvc)
• Added support for logging to tensorboard (@rolandgvc)
• Added VectorizedActionNoise for continuous vectorized environments (@partiallytyped)
• Log evaluation in the EvalCallback using the logger

Bug Fixes:

• Fixed a bug that prevented model trained on cpu to be loaded on gpu
• Fixed version number that had a new line included
• Fixed weird seg fault in docker image due to FakeImageEnv by reducing screen size
• Fixed sde_sample_freq that was not taken into account for SAC
• Pass logger module to BaseCallback otherwise they cannot write in the one used by the algorithms

Others:

• Renamed to Stable-Baseline3
• Added Dockerfile
• Sync VecEnvs with Stable-Baselines
• Update requirement: gym>=0.17
• Added .readthedoc.yml file
• Added flake8 and make lint command
• Added Github workflow
• Added warning when passing both train_freq and n_episodes_rollout to Off-Policy Algorithms

Documentation:

• Added most documentation (adapted from Stable-Baselines)
• Added link to CONTRIBUTING.md in the README (@kinalmehta)
• Added gSDE project and update docstrings accordingly
• Fix TD3 example code block