Minimal viable update for jQuery 1.9 support

**Update:** *I tried squashing the merge smaller but ended up destroying this branch. I'm trying to fix it.*

My [previous PL](https://github.com/jzaefferer/jquery-validation/pull/592) was aimed at updating the Validate library usage of the deprecated $.fn.attr() to the recommended $.fn.prop(). It lead to a bunch of difficulties so I've decided to branch. This is the minimal needed to support jQuery 1.9 and tests that passed in Chrome, Firefox, IE8 and IE9 still pass.