Integrate Path::Tiny tempdir, tempfile and rootdir

[schwern]

$scalar->path can be called on any scalar to turn it into a Path::Tiny object. What's missing is the ability to declare temp directories, temp files and the root directory. These are all class methods of Path::Tiny.

perl5i needs a way to make them available.

Having the user call Path::Tiny class methods is unacceptable as it exposes the Path::Tiny class and prevents us from providing overridden methods in the future.

They could be functions, but proliferation of exported functions is discouraged.

They could be perl5i class method calls, but we haven't discussed that mechanism yet.

Discuss.