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)

This was my logic:

1. We want people to be on the most recent version of Atom, especially in the alpha period.
2. Atom on Windows won't auto-update, so people will need to do download it manually.
3. The squirrel icon will communicate when an update can be manually installed.
4. The squirrel icon is not obviously a button and isn't synonymous with updates so we should draw attention to it.