Handle file/directory collision

[bensteinberg]

This addresses #3, where extracting a page like example.com/hello prevents the directory from being created when you go to extract example.com/hello/there.html -- I don't think it's a complete fix, as a page like example.com/bad.path will still prevent example.com/bad.path/thing.html from being created.

This PR also restores some tabs that I mistakenly turned into spaces.