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)

With the amount we release showing this tooltip every release seems a bit excessive especially since it will show for every window you open and if you are in the middle of something and don't want to update right now it could get annoying quickly.

I think the squirrel icon is sufficient to get the message across.