Added parsing for server commands, and moved it into api.

Sample slave bot is not really a thing anymore, since most functionality has been moved into `api.c` and `handlers.c`. `decode_chat_json` has been upgraded to allow server commands, i.e "/say \slot 8" from the server CLI.
Good catch for the documentation. I think `malloc` is better here since it makes the syntax cleaner, and I'm `memcpy`'ing into the entire allocated chunk anyway.