Slack API Changes

Slack's API no longer produces an `OAuth Access Token` and a `Bot User OAuth Access Token.` Reference here: 
https://gist.github.com/akhilome/6268ef912895af4224b421719e68df3c#get-your-keys. It only gives users a `Bot User OAuth Token.` This appears to be breaking changes for this package. Any chance for an update?
