README improvements

* Made it so that `@nest` was just `nest`, to avoid confusion
* Removed screenshots of the Alfred plugin, since they were missing:

![screen shot 2014-12-17 at 5 04 56 pm](https://cloud.githubusercontent.com/assets/1724000/5479831/d91125a2-860e-11e4-92ef-56e49eb30a57.png)

The download link is also broken. Maybe droplr expired the URL. This extension was Alfred 1.x anyways. Let's just remove the reference of it completely.