@link tag support

should support:

```
{@link someSymbol}
{@link http://some.url.com}
[caption here]{@link someSymbol}
[caption here]{@link http://some.url.com}
{@link someSymbol|caption here}
{@link http://some.url.com|caption here}
{@link http://some.url.com Caption Here (after the first space)}
{@link someSymbol Caption Here (after the first space)}
```

and `@linkplain` and `@linkcode` tags.

- added `linkify` Handlebars helper
- used this in the `description.hbs` template
- parse all `{@link}` tags within `@description` tags, then handoff to `linkTo` helper.  
- modified `linkTo` to support URLs and styling (if present)
- need to look in other tags too, but this is a good start.
- added test