Revert "Merge pull request #212 from miketheman/travis_github"

This reverts commit c1b81ba919505520c0004db2efb16d44a7724022, reversing
changes made to 7e26c6f72919d7eb549f5efac665e207e35faff9.

Since apparently garbage credentials don't work
Removes authentication requirement for GitHub repos

The only downside of having unauthenticated GitHub requests is that
we will be restricted to 60 per hour [1][].
If this becomes an issue, the alternative is to register the application
on GitHub, obtain a Developer Client ID and Secret, and use these for
OAuth authentication.

[1]: http://developer.github.com/changes/2012-10-14-rate-limit-changes/
Merge pull request #213 from miketheman/unauthenticated_githubs

Unauthenticated githubs