Test: changed to minimal browser test config

This minimal browser config works consistently for me locally running `grunt saucelabs`.  My testing today seems to show that Saucelabs is not able to consistently initialize browser sessions for the latest versions of Firefox and Chrome.

@nschonni @LaurentGoderre is there a way for me to test this with Travis without submitting a PR against v4.0?

Related to PR #3102.