Define a seperate JSHint configuration for NodeJS files

Summary: Currently, we assume that all JavaScript files are for use in a browser. This is not true for the NodeJS Aphlict server code. Split the current JSHint configuration into `jshint-browser` and `jshint-node`.

Test Plan: `arc lint`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11071