Compatible with mongo 3.x?

[rub1e]

I'm trying to integrate this into my meteor app; logs print correctly to console, but in the database entry the fields are all null or undefined.

I noticed this comment in the readme

Current version supports only mongodb driver version 2.x. If you want to use winston-mongodb with mongodb version 1.4.x use winston-mongodb <1.x.

Does this mean that the package isn't compatible with mongo 3.x (meteor 1.6 is up to mongo 3.4 I think)?

[rub1e]

Closing as solved by #115

Might be worth updating the README to warn users that the instructions won't work if they install the latest npm package