Fixed in-page links to match dashed (instead of underscored) header ids.

kramdown uses dashes for its [auto-generated header IDs](http://kramdown.gettalong.org/converter/html.html#auto-ids), as opposed to maruku's underscores, so multi-word intra-page glossary links weren't working after Pull #[348](https://github.com/scala/scala.github.com/pull/348)