Can't use fork
I would like to use a fork of your library while I'm not ready to send pull-request.
But when I install from fork the `lib` directory is missing

May be we could use a `postinstall` hook in `package.json` to generate the `lib` directory?
`"postinstall": "npm run prepublish"` works for me, but I wonder whether it's the right thing.

What do you think?
