put policy add PersistentOps and PersistentNotifyUrl
unit test for persistentOps
持久化参数不相互依赖
docs add persistentOps
Merge pull request #43 from dtynn/wanglin/persistentOps

Wanglin/persistent ops
putPolicy
putPolicy
Merge pull request #51 from dtynn/wanglin/putpolicy

Wanglin/putpolicy
Update CHANGELOG.md
Merge pull request #52 from qiniu/develop

Release v6.1.4