Fix youtube support.

We need to add the 'enablejsapi=1' parameter to the source URL in
order to get API events for embedded youtube iframes.  Also use the
appropriate `Player#getIframe()` API instead of the sketchy `a` field,
and play nicely in case somebody has already added a hook to
`window.onYouTubeIframeAPIReady`.
Update jquery from 1.8.3 to 1.11.1.

This fixes a bug with 'change' events on text input fields in recent
webkit versions (found with the test suite).
Update test suite; make all tests pass once more.

The doctest.js test suite had rotted a bit; made the appropriate changes
necessary to get it running again.

Removed two tests which had rotted and tested code which is unused.