Use more descriptive XCTAssert{Equal, EqualObjects, True, False, Nil}

The temporary variable assignment isn't required when using the
XCTAssertEqualObjects assertion. It seems EqualObjects is required
when comparing an array or a nillable T? type.

This uses XTAssertNil, True, or False where appropriate as well.
Merge pull request #40 from zolrath/assert-reform

Use more descriptive XCTAssert{Equal, EqualObjects, True, False, Nil}