Build: Don't assume the browser environment; smoke test on Node w/ jsdom

Refs gh-1788
Right; this is taken from my commit (https://github.com/jquery/jquery/commit/e1303a38197b36297ce6190ad318fc9e73876298) at the [standard-then-tests branch](https://github.com/jquery/jquery/commits/standard-then-tests) where the external file was actually necessary.