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

Fixes gh-1950
We need to run `grunt testswarm` on Jenkins explicitly as it needs parameters, see config of this job: http://jenkins.jquery.com/job/jQuery%20Core%20Compat%20Periodic/configure.

We could put params in env variables and use them in the `test-ci` script but I'm not convinced that's the better way.