Align API with pathlib.Path

[jaraco]

While this project has a long-established API, it's now at odds with the now more established conventions of the stdlib's pathlib module.

Let's compare the usage of a path.Path object and a pathlib.Path object and determine if it would be possible for path.Path to implement the same interface as pathlib.Path.

For now, path.Path should continue to offer its current interface, but eventually, it should drop support for duplicated functionality.

[jaraco]

Since this issue is open-ended, I'm closing it in favor of a call to action in the readme.