Reverse Playback + Revert Action

[Tia-Chen]

This branch of edits provides three new keyboard functionalities:

1. press 'p': pauses the playback
2. press 'z':

• If the game is receiving from the playback socket, pressing z reverses the playback for a couple of commands and replays the previous portion of the game. In this game state, reversing does not give the user the chance to change their actions. If user wishes to change their action, they can press 's' at the spot you wish the change to follow and use the load from file option to start a new game state.
• If the game is not in playback mode, pressing z reverts the game actions and allows for a change in command. If the game is initialized with the --record_actions flag, the record will only show the series of actions after the change without showing the history of revert.

Note: These functionalities are keyboard only currently.