zarr.open and friends should handle Path objects #601

Strictly, anything which doesn't cause os.fspath to raise a TypeError.

Minimal, reproducible code sample, a copy-pastable example if possible

import zarr
from pathlib import Path

path_str = "path/to/array.zarr"

zarr.open(path_str)  # works fine
zarr.open(Path(path_str))  # fails with TypeError because it's not a str and not iterable

Problem description

pathlib is great and everyone should use it whenever appropriate. Personally, I even subclass PurePosixPath for manipulations of object names inside hdf5/ zarr/ n5 containers.

People with zarr objects on the file system should want to use Paths to refer to them, so zarr should support people doing so.

This should just be a case of trying os.fspath on the store/path argument(s) for most of the functions in convenience.

Version and installation information

Please provide the following:

• Value of zarr.__version__: 2.4.0
• Value of numcodecs.__version__: 0.6.4
• Version of Python interpreter: 3.8.5
• Operating system (Linux/Windows/Mac): Linux
• How Zarr was installed (e.g., "using pip into virtual environment", or "using conda"): pip in virtual environment