trpl stack frame illustrations don't render correctly

On this page http://doc.rust-lang.org/stable/book/the-stack-and-the-heap.html

I see

```
| Address | Name | Value | +---------+------+-------+ | 4 | i | 6 | | 3 | c | 1 | | 2 | b | 100 | | 1 | a | 5 | | 0 | x | 42 
```

I don't think this is intended.
