Add packaging for Meteor.js, http://meteor.com

Hi David,

I'm a Meteor.js dev and volunteer package maintainer for [Meteor](http://meteor.com). Mousetrap is a great keyboard handling library, and adding it to Meteor's ecosystem will expose it to many new devs (Meteor has 20k+ stars on GitHub), likely bringing in new testers and contributors.

This PR will let you directly publish updated versions of the library 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/keypress/keypress) (Meteor's package directory). When you release new versions, you'll be able to publish them to Atmosphere by running `meteor/publish.sh`.

Thanks & best regards,
Dan, [official Meteor integrations team](https://github.com/raix/Meteor-community-discussions/issues/14)