Added "View all items" link when the selected feed doesn't have unread items


![image](https://f.cloud.github.com/assets/1084729/725408/c84bd99c-e065-11e2-8043-245cfa91aff7.png)

Here's a video comparing to Google Reader: http://www.youtube.com/watch?v=FP2fdMAoKmY (sorry, about the messed up recording).

I tried to mimic the Google Reader's behavior:

* When you add a feed it gets automatically selected, don't know if my code is correct but it works :P
* When the feed doesn't have any unread items, the "View all items" link is shown.
* When this link is clicked, all the items in the current feed are shown, but the global "mode" is kept after that.

I don't know much about javascript, hope this can be of any help, if there is something wrong, please point it out, I'll be happy to fix and  learn more about it.

Thanks.