Implement callbacks about robotjs

[ricardopolo]

Promises, async/await 👍

[kilianc]

Better if returns a promise, a callback that doesn't have err as first parameter is not standard and not yieldable :)

Looks like we have no err to report, and having always nil seems unnecessary

[skibz]

callbacks 👍

[octalmage]

This is probably way better than #14, it's the Node.js way to do things.

Thanks for the suggestion, I'll keep it in mind.

[octalmage]

I'm still not sure how I should handle this, but I think it would be best to use callbacks with a delay in the C code. This way the commands are chainable, the delay is non-blocking, and we won't run into any OS limitations.

[marcio199226]

Will be this feature implemented in any future releases ?