Shorthand expansion is busted

Here's a case where the shorthand form of `padding` behaves differently before and after inlining.

Using the styles directly, browsers set `padding-bottom: 0px` on the `<p/>`.  Juice doesn't expand `padding: 0px` to `padding-bottom`, so the `<p/>` ends up with both `padding: 0px; padding-bottom: 10px`.

Anyone else caught by this?  My only idea for fixing it is to expand shorthand properties as they're [parsed])(https://github.com/LearnBoost/juice/blob/master/lib/juice.js#L112).  This could balloon style length.  Might be worth another pass after inlining to combine styles back into shorthands where it's safe.  Thoughts?