Fixing verifyNoInteractions result when stubbing method -Mark

I'll leave this PR up for discussion. Here's my scenario, in case there's a better way to do this:

In my `setUp`, I have a universal stub, something like `[when(mock.foo) thenReturn:@"bar"]`, that gets called for each test. However, `SBLVerifyNoInteractions(mock)` no longer works in the test methods of that file because of the previous stub.

My proposed solution is to remove the `sblNumberOfInvocations` property and verify that the mock is not called by counting the number of `sblActualInvocations`. I've added a unit test to reproduce my issue.