------------------
Features
~~~~~~~~
- Support multi-level nested key. [qin_hw]
- Remove api of attribute. [qin_hw]
- Add class attribute. [qin_hw]
- Implement yaml config manager. [qin_hw]
BREAKING CHANGE
~~~~~~~~~~~~~~~
- Update project url. [qin_hw]
- Rename package name from yamlconf --> ymlconf. [qin_hw]
- Rename package name from yamlconf --> ymlconf. [qin_hw]