Public scoped package

[arunasank]

I think if this was scoped to the @mapbox namespace and published with public access, by default everyone at Mapbox would have access to publish to the package per https://docs.npmjs.com/cli/access. 🙂

Ref: #24

cc/@aarthykc

[drboyer]

We should still do this, just to be consistent with other Mapbox packages.

/cc: @mapbox/platform