Support for Node 12/master

[mcollina]

It seems this module has not been updated to support Node 11, and I've a fear it might not be working on Node 12/master. It's not even in CIGTM.

Because of the critical importance for older packages, can somebody expert on this check it out?

[Flarna]

Regarding Node 11 NAN works fine. I created #830 to update readme and CI matrix.
But for Node 12 there is something to do as APIs have been removed/have been deprecated.

[kkoopa]

I just published a long overdue update, but it does not address Node 12.

[reconbot]

@mcollina is nan not important for newer packages too?

[mcollina]

I think nan is important for existing packages. We can’t expect packages to migrate to napi in a short timeframe.