Support yarn

[vladimyr]

This resolves #195 by supporting following scenario:

$ NPM_CHECK_INSTALLER=yarn npm-check

Also if yarn's lockfile has been found it will be used as default package manager 🎉

[vladimyr]

Those build failures are due to node@4 lacking es6 support...

[hacknug]

@dylang any chance this could be reviewed and merged? For some reason, yarn upgrade-interactive isn't as reliable for me as your package 🤷‍♂

[VincentLanglet]

@dylang This would be great

Edit: It seems there is another PR https://github.com/dylang/npm-check/pull/365/files

[dkhunt27]

Merged with #397

[fschoenfeldt]

By the way, by using NPM_CHECK_INSTALLER=yarn npm-check, yarn tries to install via yarn install which doesn't work anymore:

? Choose which packages to update. [email protected], [email protected], [email protected], babel-plugin-styled-compo
[email protected], [email protected], [email protected], [email protected], [email protected], [email protected], gatsby-plugi
[email protected], [email protected], [email protected], [email protected], gatsby-plugin-styled-compon
[email protected], [email protected], [email protected], [email protected], [email protected],
 [email protected], [email protected], [email protected]

$ yarn install --save [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] --color=always
Command failed: yarn install --save [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] --color=always
warning ../../package.json: No license field
error `install` has been replaced with `add` to add new dependencies. Run "yarn add [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected]" instead.

For more detail, add `--debug` to the command

For now, I just run the suggested yarn add ... command. 😄