Summary:
Fixes test execution for open source:
- adds hamcrest jar and dependency, as required by buck (to not throw `"Unable to locate hamcrest on the classpath. Please add as a test dependency."`)
- enables events for OSS, to make tests pass
Reviewed By: SidharthGuglani
Differential Revision: D16202542
fbshipit-source-id: a56069de162f739b3b989961b5dc00f3d37f5849