deadzones quitting without a beep when -p above certain threshold

```
deadzones -s fa -k 50 -o data/deadzones/hg38.deadzones -p 40 data/genome/hg38/chroms
```

and then it quits after a minute. If I reduce the `-p` to 30 it keeps on going.

Also, how are deadzones computed? There are blazingly fast kmer-counters out there, I might be able to throw together a script for computing deadzones using one of them if you could explain how you do it.
