Private methods made protected so they can be extended

[bkuhl]

Currently it's not possible to extend DiscordClient and overwrite the constructor without copying all of these private methods and nearly the whole class. making these protected allows it to be more extendable.

[bkuhl]

I was able to work around this problem, but in a bit of a sloppy manner since there's no way to detect if you're being rated limited by looking at the http status code of $this->discord->channel->createMessage($requestData);. You have to look at the response body.