samples/extract_streams.py not compatible with lib

```
$ python samples/extract_streams.py  ../t.aff4 
Traceback (most recent call last):
  File "/home/r/pyaff4/samples/extract_streams.py", line 18, in <module>
    with zip.ZipFile.NewZipFile(resolver, volume_path_urn) as volume:
TypeError: NewZipFile() missing 1 required positional argument: 'backing_store_urn'
```

Indeed, NewZipFile required 3 arguments