Should have fs.realpath*.native() function

[gucong3000]

• https://nodejs.org/api/fs.html#fs_fs_realpath_native_path_options_callback

[coveralls]

Coverage increased (+0.01%) to 85.714% when pulling 347b87d on gucong3000:realpath_native into a32c852 on jprichardson:master.

[manidlou]

That's right we have to add that! But wondering if we explicitly have to add that to the api!

[RyanZim]

We should support fs.realpath*.native() but this isn't the way to do it. We've got to support both promises and callbacks.