Avoid extra bottom padding when using jQuery 1.8+

I was getting lots of extra bottom padding in my rows, which was equal to the "cell" padding * 2.

The solution is to use `$.css('height')` instead of `$.height()`, which takes the current `box-sizing` into account, per the comments at http://api.jquery.com/height/
Merge pull request #12 from sbleon/master

Avoid extra bottom padding when using jQuery 1.8+