Add tests for contact model
Add tests for contact model

Summary: Added some basic tests (inspired by those in the event-spec.js) for the contact model

Test Plan: tests

Reviewers: mark, halla, khamidou

Reviewed By: mark

Differential Revision: https://phab.nylas.com/D6167

nylas/nylas-nodejs,nylas/nylas-nodejs,nylas/nylas-nodejs