Add Test for Tar File with Missing Parent Dir Entries.

I created a small `tar.gz` with a single entry: `test/lib/test.txt`. There are no parent directory entries and this reproduces the issue I had a few days ago. The test failed prior to PR #5 but with PR #5, it passes successfully.

For the record, I created the `tar.gz` following some ideas taken from http://superuser.com/a/219070.