Support for natural language communication between players.

[fringsoo]

It would be great if the natural language messages from the chat box could be added into the observation / action space of the agents.

[vshallc]

This is available after 389d246577e7bbc9f253618fea6e0fb1d173d829 in branch dev now.

The text from chat box can be get from observation['game']['messages']

and the message can be sent by assign text value to action['player']['message'].

Some functional prefixes in sending messages:

• .: send this chat message to all allies, e.g. .Hello all my friends! (all your allies can see this message);
• :: send this chat message to a player, e.g. Alice: Hello Alice (only player Alice can see this message);
• >: prevent special symbols being filtered by the system.