Title of link label definition mapped to html

[grunt-markdown](https://github.com/treasonx/grunt-markdown) transforms

```
[google]: http://google.com
"GOOGLE"
```

to

```
<p>GOOGLE</p>
```

while according to [daringfireball](http://daringfireball.net/projects/markdown/dingus) it should not create anything at all in the `html`.
