unused async await

[MathieuDerelle]

I had a "ReferenceError: regeneratorRuntime is not defined" when using your package because I had to add it to my list of transpiled npm packages

I looked a bit at your code and the async await statement doesn't do anything since there is no await airbrakeNotify

https://github.com/alexcastillo/redux-airbrake/blob/bcbbfe4996262a3c67d9614bfd9a98ab7ca9906f/src/index.js#L36