Fixes jQuery 1.9+ issues with hover and HTML strings

Fixes jQuery errors:
  - "hover" pseudo-event is deprecated for "mouseenter mouseleave"
  - HTML strings must begin with less-than character

See the [jQuery 1.9 upgrade guide](http://jquery.com/upgrade-guide/1.9/).

Tested against WP nightlies. From all indications, WP 3.6 will ship with jQuery 1.9.1 or greater (see the [Trac ticket](http://core.trac.wordpress.org/ticket/22975)).