Ensure project has ample test coverage

[jaraco]

• Re-use compose from jaraco.functools.
• Remove exception handler for 'Python bug', apparently no longer relevant as it goes back at least 12 years.
• Remove another unused block.
• Remove fspath as it is unneeded as Path is a str subclass. Add a test to capture expected behavior.
• Add test for normpath
• Add test for expandvars
• Add test for .expand
• Add test for splitdrive
• Expand test to ensure the result is a Path. Fix test and make both parts Path objects.
• Remove unc functions, removed in Python 3.7 (bpo-29197).
• Add test for parts
• Add test covering relpathto
• Add tests covering walk. Fix bug in walk when errors are ignored.
• Add test covering write test. Fix resulting failures.
• Add test covering read_md5
• Add test covering read_hexhash
• Add tests for isabs and ismount
• Implement samefile universally.
• Add test for last access time
• Add test for access
• Add tests for stat and lstat
• Add a note in the readme about intentions for API convergence. Fixes Align API with pathlib.Path #185.
• Add test for get_owner. Suppress coverage checks.
• Add tests for statvfs and pathconf
• Add test for utime. Allow utime to accept all parameters.
• Add test for chmod as a str
• Disable Python 3.10 tests
• Hide chown when not available, similar to other methods.
• Assume pwd and grp are present if chown is.
• Add test for chown
• Add test for renames
• Add test for mkdir_p
• Add test for removedirs_p
• Remove duplication of remove/unlink.
• Define link functions unconditionally.
• Add test for link
• Add test for symlink with no parameters
• Add tests for readlinkabs
• Collapse branchy return
• Add tests for chroot and startfile.
• Add test for invalid write mode.
• Add test for _permission_mask with invalid input.
• Add tests for Handlers
• Exclude compatibility module from coverage testing.
• Improve coverage in test module.
• Update changelog.