Upgrade to Meteor 0.8.1 (DDP improvements, security fixes for oauth).

Meteor release notes:
https://www.meteor.com/blog/2014/04/30/meteor-081-important-oauth-update
https://github.com/meteor/meteor/blob/release/0.8.1/History.md

Change-Id: I1586c4a5ec64e01ce4502b8634eaa5e6d9fb64ca