Merge pull request #35 from liluo/dev

增加关于 scope 的说明
Merge branch 'master' of https://github.com/douban/douban-client
fix: 调用 delete 类 API 时报 ValueError #36
Merge pull request #37 from liluo/dev

bugfix: 调用 delete 类 API 时报 ValueError #36
refs issue #38
refs issue #38
Merge pull request #39 from tianyu0915/master

refs issue #38
Now it is able to call unauthorized APIs which do not require authorization
Merge pull request #40 from messense/feature-unauthorized-api

Make it able to call unauthorized APIs which do not require authorization