Use strict mode for Javelin core

Summary: Enable strict mode for Javelin when running in NodeJS.

Test Plan: Made sure Aphlict still worked.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11432