Uninformative error when passing `pathlib.Path` to `pyBigWig.open`

[rcalef]

First, thanks for providing this library to access BigWig files programmatically through Python code!

Description:
I was trying to test out the library using a path stored as a pathilb.Path and it looks like the library doesn't currently support this.

Example:

from pathlib import Path

my_bw_path = Path("/path/to/track.bw")

# Raises the exception:
#  RuntimeError: Received an error during file opening!
bw =  pyBigWig.open(my_bw_path)

# Works fine
my_bw_bw =  pyBigWig.open(str(my_bw_path))

This is an easy fix on the user side, just hard to know that Path vs str is the issue given the error message.

This is with pybigwig==0.3.25.

Thanks!