Remove a bunch of hacks and quirks from jquery.gravy
We have a number of hacks and workarounds for old versions of web browsers

(mostly IE6). Since we no longer support these very old browsers, we can clean

a lot of this up. My goal here is to eliminate reliance on $.browser, since

that's blocking us from upgrading to more recent versions of jquery.
The one hack that I didn't remove from djblets is a fix for the innerHTML quirk

in IE. This quirk was fixed in IE9, but for now we still want to maintain

compatibility with IE8.

Smoke tested changes in a few different browsers. Checked that hover for

tooltips still worked.