Tweak hostnames table

* Introduce a glossary link style that is set back from the content,
and isn’t so obtrusive
* Add borders to the table in keeping with other table styles
* Fix invalid HTML tag type
* Always put default hostname onto a new line

![screen shot 2014-03-14 at 14 51 44](https://f.cloud.github.com/assets/319055/2421902/30042ba0-ab88-11e3-9e80-f8f7d72aeb20.png)