Added helper functions for channel and user lists to make the API a bit ...

...more friendly

Added support for the following methods: chat.delete, chat.update, channel.history, channel.list, users.list, auth.text, channels.info, channels.invite, channels.join, channels.leave, channels.mark, channels.setPurpose, channels.setTopic, emoji.list, stars.list

I hope you'll forgive a slight reordering of some of your original code
Constructor shouldn't be performing any implicit actions.

Perhaps move these two functions that make external calls to a separate function, such as `setup()` or `init()` that the user can call.