Enhancement/environment

[chunming-c]

Enhancement

lerna bootstrap with default npm instead of yarn to prevent from issue that caused by older version of yarn

• lerna bootstrap after module install
• remove all the yarn.lock in folder packages

[AllenFang]

Seems like some people do have commit package-lock.json to repo but some people is not...

https://stackoverflow.com/questions/44206782/do-i-commit-the-package-lock-json-file-created-by-npm-5

so any concern that why we avoid to commit package-lock.json to repo?

[chunming-c]

The reason why I skip package-lock.json is that I want to keep our repo maintained by one package manager, that is yarn. Therefore, that's the reason why I omit this.

ref: https://github.com/babel/babel/blob/master/.gitignore#L13

[chunming-c]

However, you may be curious about why I remove all the yarn.lock in folder packages.lerna seems to have some problem with elder yarn version. Therefore, I decided to bootstrap with npm by default instead of yarn. Once yarn has become more stable then correct the version.