Automatically run tests against multiple jQuery versions

This PR resolves #176 as well as adding some additional functionality. The basic idea is to make running tests against multiple jQuery versions easier. To do so, I've added two integrations: one for grunt and one for QUnit through a visual browser.

IN GRUNT we can now run `grunt test` and all tests will run against all supported versions of jQuery as documented in the Gruntfile task config. Additionally there are smaller subsets to run against such as `grunt test:oldestAndLatest` to test against our oldest and latest supported versions.

IN A BROWSER there is now a button in the header to run all tests for the list versions of jQuery in that header. Basically it waits for the `QUnit.done()` callback then redirects the user to the next link in the page based on their index in the header. This is finicky because we already dynamically load the jquery version, so we have to wait for that, and QUnit rebuilds that header (ugh) so we have to delay our binding to the button. I have it working in most cases, and it will stop the auto-redirection if any test fails.

Opinions welcome!

(Tagging @dcneiner or @jcreamer898 for some verification before merging.)
@jakerella Can we not just use a delegated event on `document` to avoid this onload/dom-ready/setTimeout setup?