COMPAT: Add Pathlib, py.path support for read_hdf
- [*] closes #xxxx
- [*] tests added / passed
- [*] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

Closes #11773

Travis-ci test JOB_NAME=27_slow_nnet_LOCALE consistently fails due to locale issue...  zh_CN.GB18030??
