The dependency bound on `directory` is too loose

[mniip]

tar 0.6.4.0 and 0.7.0.0 build-depends on directory >=1.3.1, however it uses System.Directory.OsPath which is only available in directory >=1.3.8.0.

Older versions of tar are fine.

[Bodigrim]

Could you raise a PR? I'll make Hackage revisions afterwards.