Reduce jQuery dependencies in tests

I've been experimenting with working around Backbone's (light) jQuery dependency (see #237, [scoliosis](https://github.com/paulmillr/scoliosis) and others), and it'd be great if the tests had as light a requirement on jQuery-specific features as possible (no more than the library itself does).

* Remove $(document).ready from tests in favor of scripts-at-the-bottom and an IIFE
* Change a jQuery-specific selector `p:has(a)` to two separate tests

Should make it easier to test with Zepto, adapters for [MooTools](https://github.com/inkling/backbone-mootools), [d3](https://github.com/akre54/backbone-d3) and other jQuery-like APIs.