As of gh-2338, if one has loaded the jQuery MouseWheel plugin, the `mousewheel` handler would fire the `wheel` one, but the `wheel` one would also run in response to the native `wheel` event, resulting in double the distance handled by the spinner. To prevent the issue, only fire the `wheel` handler from inside the `mousewheel` on if the event was triggered by jQuery - jQuery will not care that the underlying event is `wheel` and will only fire handlers for `mousewheel`. Also, add an iframe test using jQuery MouseWheel to not affect all the other tests. Plus, migrate from `QUnit.reset` to `QUnit.done` (see qunitjs/qunit#354). Closes gh-2342 Ref gh-2338