Allow windows users to download Atom via the release notes view

![release notes - _users_corey_github_release-notes](https://cloud.githubusercontent.com/assets/596/3513392/43a750c0-06c2-11e4-8f44-4d7f91f87a07.jpg)

If you want attention drawn to it, how about just showing 'Update Available' instead of the squirrel icon in the status bar?