List of adopters needs updated

The front page reads:

```
The Activity Streams format has already been adopted by BBC, Gnip, Google Buzz Gowalla, IBM, MySpace, Opera, Socialcast, Superfeedr, TypePad, Windows Live, YIID, and many others.
```

Out of those, Google Buzz and Gowalla no longer exist, and Windows Live and YIID have changed names.
