Version 0.2.0

• New graph neural network building blocks (message passing based on torch-scatter in addition to existing graph convolutions)
• Support for action recording, replay from pre-computed action records and feature collection.
• Improved wrapper hierarchy semantics: Previously values were assigned to the outermost wrapper. Now values are assigned to existing attributes by traversing the wrapper hierarchy.
• Removal of deprecated modules (APIContext and Maze models for RLlib)
• Reflecting changes in upstream dependencies (Gym version pinned to <0.23)