System tests for events creation

Summary: This is a simple smoke test to check that event creation and deletion works. I'll be interested in your thoughts on whether it's necessary to test syncback (e.g: by connecting to the google backend and querying directly).

Test Plan: Ran the tests

Reviewers: emfree, kav-ya

Reviewed By: kav-ya

Subscribers: spang

Differential Revision: https://review.inboxapp.com/D772