compatible: let this module works on 0.10.x and 0.11.x

hi, @dinhviethoa

I use nan to rebuild this module, and it works fine on 0.10.x and 0.11.x.
Plus, I added the new api from #12, that would only expose etpan to `node-mailcore` and added some tests for them, then I think a `.travis.yml` is necessary for now?