Use containers for testing again

[dfreedm]

Disable chrome security sandbox due to travis-ci/travis-ci#8836

Remove node module caching with the removal of package lock

[TimvdLippe]

Okay with the containers, but I am not sure about the cache change. If I understand correctly, it checks for existence of the exact version of these npm packages. Package.lock or not, the cache should be faster and safe to use?

[dfreedm]

If we're not using package-lock, I'm not sure having the npm cache is a great idea. The only way the installed modules will update now is if we push updates to package.json.

But it is worthy of a bit of debate.

[TimvdLippe]

Before npm introduced the package lock, we were using the cache as well. I don't recall any problems back then. Per https://docs.travis-ci.com/user/caching/#Things-not-to-cache Travis advises to use the cache especially for npm.

[dfreedm]

SGTM