N-API support

[NickNaso]

Hi @charliegerard I watched your talk at JSConfEU and I tried to port this module to N-API using its C++ wrapper node-addon-api.
You can find my work here: https://github.com/NickNaso/Epoc.js/tree/napi
If you want experiment with N-API you can create a branch and call it "napi" so I can execute the PR on it.
After that we can iterate to over it and at the end publish a new version of epocjs or a tagged version like reported here: https://nodejs.org/en/docs/guides/publishing-napi-modules/
I'm involved on the N-API team and this porting is part of our effort to understand which are the common api that developers need to implement native add-ons.
If you don't want to take dependency on N-API I understand. If you want give me a feedback it should be great.
I will be happy to contribute and help in any way.