According to the documentation you can add a project from the registry or from a tarball url?
# add plugin from plugin registry
meteor add cordova:org.apache.cordova.camera@0.3.1
# add plugin from the tarball url
meteor add cordova:com.phonegap.plugins.facebookconnect@https://github.com/Wizcorp/phonegap-facebook-plugin/tarball/0e61babb65bc1716b957b6294c7fdef3ce6ace79
So how do I add this plugin off of github?