cross-ci/lib/echo.js

`cross-ci` standardizes environment variables for CI. For example, your can simply use `BUILD_BRANCH` variable in all CI runners instead of `CIRCLE_BRANCH` in CircleCI or `TRAVIS_PULL_REQUEST_BRANCH` in Travis.

const name = process.argv[2];

// eslint-disable-next-line no-console
console.log(process.env[name]);