native.js is not passing tests in Firefox and Safari with built-in classes like HTMLElement

[trusktr]

In Lume, we made tests also run in FF and Safari, but it fails due to native.js not handling HTMLElement (etc) well in FF and Safari, so we undid FF and Safari testing for now.

Lume is not using this feature, but it prevents tests from passing.

The cli change: https://github.com/lume/cli/commit/d37cabbef0db59a221cc6538ea449745528856f3