add warning of utf8 keys
Merge pull request #71 from longshanksmo/develop

add warning of utf8 keys
add comment of download domain
Merge pull request #73 from longshanksmo/develop

add comment of download domain
resumableio: use mkfile
Merge pull request #76 from chzyer/develop

resumableio: use mkfile
Update CHANGELOG.md
update putpolicy
Merge pull request #78 from coaku/feature/b_xzk_update_put_policy

update putpolicy
Update CHANGELOG.md
add unitest for putpolicy
Merge pull request #79 from coaku/b_xzk_add_putpolicy_unitest

add unitest for putpolicy
1. catch ret None issue in rsf.py
2. make param expires optional for GetPolicy in rs/rs_token.py
Add Title for docs/README.md.
fix test
Merge pull request #83 from SunRunAway/develop

fix test
Merge pull request #82 from BluntBlade/develop

Add Title for docs/README.md.
Update rsf.py

``if not ret.get('marker'):`` 在ret为``None``时会报错。
bug fix
fix