i18n support

I have noticed that standard chamelon i18n support is not working while using pyramid_skins. 

```
<html>
  <body i18n:domain="mydomin">
    <p i18n:translate="">My title</p>
  </body>
</html>
```

The above example works fine (message is translated) when rendered directly by pyramid.
It doesn't work when I use _renderer='skin'_.
