Export promisified methods

[Naktibalda]

This middleware uses bluebird promisify functionality internally, but if I want to use promises in my bot code, I have to promisify it again.

Would it be OK to export promisified methods?

[germanattanasio]

I think we can support callbacks and promises with the same function. See https://loige.co/to-promise-or-to-callback-that-is-the-question/