Fixed glibc fault because gzclose bad pointer

@tzcoolman, please try things through when commiting to master, otherwise:

https://travis-ci.org/SciLifeLab/facs/builds/5288215

Also, the commandline interface for ./facs query needs fixing:

```
$ ./facs query

Usage: ./facs query [options]
Options:
	-r reference bloom filter to query against
```

Query takes 2 arguments, there is only one named in the help file! :-S