Release v1.6.0 and bug fix for TRPO (Stable-Baselines-Team#84)

Release v1.5.0 (Stable-Baselines-Team#64)

Update release date

Release 1.3.0 (Stable-Baselines-Team#48)

Train/Eval Mode Support (Stable-Baselines-Team#39)

* switch models between train and eval mode

* update changelog

* update release in change log

* Update dependency

Co-authored-by: Antonin Raffin <antonin.raffin@ensta.org>

Release v1.1.0 (Stable-Baselines-Team#34)

SB3 v1.0 (Stable-Baselines-Team#23)

Bug fix for QR-DQN (Stable-Baselines-Team#21)

* Bug fix for QR-DQN

* Upgrade SB3

Upgrade SB3 (Stable-Baselines-Team#20)