Fix Error Unpacking Certain Tar Files.

I was trying to use `unzipit` today and my test archive was https://repo.wibidata.com/artifactory/kiji/org/kiji/schema/kiji-schema/1.5.0/kiji-schema-1.5.0-release.tar.gz. This was failing to unpack with this error when trying to unpack in `dependencies`:

```
open dependencies/kiji-schema-1.5.0/lib/kiji-schema-platform-api-1.5.0.jar: no such file or directory
```

I'm not exactly sure what the problem is but it turns out that when iterating on the entries, we get to the jar file but we haven't iterated over kiri-schema-1.5.0 and lib yet. So the parent directory doesn't exist and the file creation fails. So I added creation of the parent directory of file entries. 

I haven't been able to create a fixture file that reproduces the problem but this fix does result in successful unpacking of that `tar.gz`.

I thought I'd post this even though I don't have all the answers. 
Nice catch on conserving the original file permissions.