Add correct relegation lines

This solves the semantics of where a relegation line should be .

It also solves the problem of keeping `border-collapse: collapse;` but also showing the relegation line (they weren't showing on embedded tables).

It is now also consistent with the embed tool.

## Prove it
![relegation-lines](https://cloud.githubusercontent.com/assets/31692/2718055/5148985c-c549-11e3-9c4b-f2edde537553.png)

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![Magic innit](http://greyscalegorilla.com/blog/wp-content/uploads/2011/12/Stripes3.gif)