assertEquals → assertSame in unit tests

Summary:
The tests now use assertSame to assert type is respected too.

We keep assertEquals in EventServiceProviderTest::testOmittedFiles,
as we there compare two arrays, regardless of the order of the items.

Test Plan: phpunit

Reviewers: dereckson

Subscribers: alken-orin

Differential Revision: http://devcentral.nasqueron.org/D281