Travis CI fails for last 10 PRs on this repo with same error

[etnichols]

I recently opened #224 to update project README. I saw Travis CI run and fail with the following error:

24.75s$ yarn
yarn install v1.15.2
[1/4] Resolving packages...
[2/4] Fetching packages...
info fsevents@1.1.2: The platform "linux" is incompatible with this module.
info "fsevents@1.1.2" is an optional dependency and failed compatibility check. Excluding it from installation.
error phantom@4.0.12: The engine "node" is incompatible with this module. Expected version ">=8". Got "6.17.1"
error Found incompatible module
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.

Direct link: https://travis-ci.org/KyleAMathews/typography.js/jobs/562359426.

Upon further investigation, it appears the last 10 PRs on this repo all experienced same Travis CI failure: https://travis-ci.org/KyleAMathews/typography.js/pull_requests.

[etnichols]

Related: ember-cli/ember-cli#8360