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.
The patch is just sitting in there to keep unit test output clean. incr_counter emits output to stderr when an event is not parseable (IIRC).