tfoot before tbody

[ghost]

Hi! Just a minor one. Line 101 of _debug.scss doesn't apply in HTML5, since the spec has changed to allow for tfoot elements to appear after the tbody.
http://www.w3.org/html/wg/drafts/html/master/single-page.html#the-tfoot-element

[theuiguru]

Isn't tbody the same thing as table, tr, and td though? Curious to know the real difference between them. I can't seem to figure out why it's used.

[csswizardry]

Please see #291.

Thank you.