Typo: it should be 'uri' not 'u'.

Hey,

I just tried to play with extension, which is very cool. But it seems you need minor modification.

Have a look at my proposed changes.
![Error Screenshot](https://cloud.githubusercontent.com/assets/2670622/2755796/a5cea5ba-c96d-11e3-9e51-334c572b95a4.png)

Thanks!