Regression tests on Node

We need to test QUnit HEAD in `lib` directory every time to detect regressions immediately.

First I tried to use `node-qunit` for this purpose, however node-qunit uses git-submoduled QUnit, so the QUnit object run by node-qunit is not fresh enough. It is not good for development of QUnit itself. Using `qunit` npm module does not mean testing `qunitjs`. So I wrote a simple grunt task to test QUnit HEAD on Node.

Please note: `require('qunitjs')` fails until merging https://github.com/jquery/qunit/pull/401

When merging is done, running against `test/test.js` and `test/deepEqual.js` then result is:

    >> 308 assertions in (1709ms), passed: 296, failed: 12

12 failures are due to absence of browser related objects(window, document).

It would be better to use JUnitLogger reporter or TAP reporter to integarate with Jenkins.

This pull-request is related to https://github.com/jquery/qunit/pull/401 and https://github.com/jquery/qunit/issues/400