Pull in changes from boxen/our-boxen

I need the GitHub two-factor auth stuff in here.

I'm getting a few dozen warnings about failed dependencies, even after running `librarian-puppet install`. All of the form:

    Notice: /Stage[main]/Ruby::1_8_7_p358/Ruby::Version[1.8.7-p358]/Ruby::Gem[bundler for 1.8.7-p358]/Rbenv_gem[bundler for 1.8.7-p358]: Dependency Repository[/opt/boxen/rbenv] has failures: true
    Warning: /Stage[main]/Ruby::1_8_7_p358/Ruby::Version[1.8.7-p358]/Ruby::Gem[bundler for 1.8.7-p358]/Rbenv_gem[bundler for 1.8.7-p358]: Skipping because of failed dependencies