Remove 'osx' from travis settings (#513)
Remove 'osx' from travis settings (#513)

* Mac tests run at GitHub Actions.
* Improve node version specification.
    * https://medium.com/@nodejs/choosing-the-node-js-versions-for-your-ci-tests-hint-use-lts-89b67f68d7ca#5e43
    * Since GitHub Actions is also testing, `node` and `lts/*` are specified.
motdotla/node-lambda,teebu/node-lambda,teebu/node-lambda,motdotla/node-lambda