suspected bug in "num_filters_passed" #126

First, thanks a lot for the amazing work on boltzgen and making it fully available for the community!

Here I assume "num_filters_passed" should count the number of passing filters, but really it's inside the loop over filters and increments by 1 each time all the filters up-till-now are passing.
I think that's not the intention, hopefully I'm not missing something.