Switch all libs over to using Path::Tiny instead of Path::Class

This is due to this bug in File::Slurp -
    https://rt.cpan.org/Public/Bug/Display.html?id=83126
as well as the fact I am making a wild guess and trying to solve failing tests
on windows (#16).
Tests no longer use Path::Class
Merge pull request #18 from kablamo/path-tiny

Switch everything to Path::Tiny