Pfio

Release notes:
- 151 File Access V2 API (experimental)
- 152 AWS S3 API Support (experimental)
- File Access V2 API addresses lots of past bugs and issues.

- Python 3.5 support dropped and 3.9, 3.8 added
- Raise `IndexError` instead of assertion ( 136 )
- Introduce physical size limit to file cache ( 143 )
- In FileCache, index file and data file are merged to one ( 145 )
- Change behaviour of size limit exceed, and allow cache file overwrite (138)

This release came into real definitely by belltailjp . Thanks a lot!

Major changes include:

Documentation and Style
1. Replace 'an URI' with 'a URI' (121)
2. Fix typo (122)
3. Fix style (127)
4. Test documentation with Python3.7 (132)
5. replace 'github.com/chainer/pfio' with 'github.com/pfnet/pfio' (125 )

New feature
1. MultiprocessFileCache for efficient and easy cache with pytorch dataloader (num_workers>0) (128)

The initial `pfio` release after renamed from `chainerio`.

Major changes include:
New Features:
1. Renamed to `pfio` from `chainerio`. Import from both name are supported to keep the backward compatibility 118
2. New designed unified `Filestat` object 114 (thanks to belltailjp !)

Minor update:
1. Document grammatical update 121

Major changes include:

Bugfix:

- Test fails when KRB5_KTNAME is not set 103
- Close and reopen shared zip after forking based on pid 105
- Fix HDFS unittest 108
- list and isdir for non-directory-included zip 112

Dependency:
- Upgrade required `krbticket` version to 1.0.5 107 113 115

Refactoring:
- Refactoring test_zip_container to use parameterized 116

This release is a bugfix release:

Bugfix

Get correct principal name when keytab is given 97
Use krbticket 1.0.2 to avoid issues when the keytab is not given 96