remove non-core deps (as advertised)

This removes the non-core dependencies as advertised in the documentation:

  - Dir::Self, in this case I think FindBin will do, and it is in the core
  - Log::Fu, which I think was intended to be optional, but version 0.25 is still required if it is used
  - Archive::Tar instead of Archive::Extract, since the latter is being removed from the core in 5.20 (according to corelist)

Also added a .gitignore and MANIFEST.SKIP