Added safejs pattern which is more just error handling approach

[sergeyksv]

Well, I personally like async await (loved it after C#), so safejs is ore for curiosity as something between raw callbacks and promises. It is still callbacks, but much more handy with error handling. Our way to convert callback hell to just callback pattern :)

[kyrylkov]

@sergeyksv Thanks for the PR, however I'm not going to land it. The purpose of the repo is not to demonstrate and compare different approaches to async in Node.js. It is to measure async function and native promise performance in comparison with bluebird promises and callbacks in different versions of Node.js

You might want to create a PR here https://github.com/petkaantonov/bluebird/tree/master/benchmark