…fers and data classes

- Rollback PPO changes and sync up with latest round of changes
- Updated PPO to use the PPOReplayBuffer, PPOTransition, and PPO TransitionBatch
- Update Lunar Lander Tutorial with BasicReplayBuffer and PPOReplayBuffer
- Update Tutorials to use new replay buffer

…int.ipynb

Updated Unit Test to reference new location of important class and breaking PPO into 2 separate files with a new base class