Add packaging for Meteor.js.

Hi Mike,

I'm a package maintainer for [Meteor.js](http://meteor.com), the [most popular full-stack JavaScript framework](http://github.com/meteor/meteor).

Meteor devs love d3. It was a [core package](https://github.com/meteor/meteor/issues/2557) until recently, and now it's time to separate concerns and let the community maintain the Meteor <-> d3 integration. This PR will allow you to directly publish updated versions of d3 as they become available. All you have to do is create an account at https://meteor.com/ (click *SIGN IN*, then *Create account*). After you've done that, please let me know the name of the account, and I'll add you as a maintainer.

I've already published the current version of the package on [Atmosphere](https://atmospherejs.com/d3js/d3) (Meteor's package directory). When you release new versions of d3, you'll be able to publish them to Atmosphere by running `make meteor`.

Thanks & best regards,
Dan