Add support for Meteor 3

[dallman2]

Hello,

This repository needs to be updated to support Meteor 3. In my application, I have cloned this repo and commented out the api.versionsFrom('1.4'); in the package.js file. Can the Meteor 3 API level please be added to this call? As in:

api.versionsFrom(['1.4', '3.0-beta.0]);

or just remove it entirely.