Replaced callbacks with async/await. Used axios for async HTTP request.

[andrunix]

[pste]

I love the modernized approach but this is a breaking change. I think at this point that your pull must include a change in major version (2.0.0).

The other approach in my mind: module.exports { retrieve, retrieveAsync // <== the new call } has to be avoided at this point :)

If you add it I'll check and merge. Thanx!