Replace crossLink with a markdown link.

For some reason the crossLink helper is not rendering correctly.
![screen shot 2013-09-10 at 2 09 25 pm](https://f.cloud.github.com/assets/54056/1116897/3a27408e-1a44-11e3-88ec-c775f05069a0.png)

Link using markdown:
![screen shot 2013-09-10 at 2 07 07 pm](https://f.cloud.github.com/assets/54056/1116898/3a2fab0c-1a44-11e3-8646-0afd20543c4b.png)

I also added a link to the `link-to` docs from the `linkTo` docs.