Clarify that allstar must be able to access the .allstar repo

[jeffmendoza]

Suggestion:

1. Install the Allstar app.
2. Enable the Allstar app Repository Access to your ".allstar" repository, so that your site configuration can be read by the app. You must also provide Repository Access to every repo you want Allstar to monitor. For ease of initial configuration and subsequent administration, We [strongly] recommends that you simply choose "All Repositories" under Repository Access, even if you don't plan to use Allstar on all your repositories.
3. [...]