Get public repo without authentication

[drahoslove]

It would be really nice, if GET /repos/:owner/:repo could succeed without authentication for public repos. Similar to issue #23.

[Corben78]

Same for organizational repos, their issues, milestones, etc.
As they are visible from the webinterface without authentication, the api should also be able to access them without authentication.

[unknwon]

This should have been fixed already.