Benp/add total event count

@rocha @brianhw @mulby 

I think it makes sense to get started on review. For now, could you ignore (or at most, skim) the test files? 

The prod code is worth a closer look at this point, and I welcome any feedback.
There's not that I saw. This is definitely an area for refactoring. The various test classes that use this implement it in slightly different ways (e.g., different fields are being populated).