Replace IO::All and Path::Class with Path::Tiny.

This should make dealing with paths somewhat more straight-
forward and reusable.
Merge pull request #145 from duckduckgo/mwm/tiny_paths_all_alike

Replace IO::All and Path::Class with Path::Tiny.
Make sure we check the file we're copying exists
Merge pull request #147 from duckduckgo/zaahir/fix-duckpan-server

Make sure we check the file we're copying exists