Fix unit tests on fresh checkout.

`bundle exec rake` should run with no errors on ruby-2.0.0-p353 which is
the same version embedded in vagrant 1.6.5 on Windows.

The section "Checking Your Code into Version Control" on http://bundler.io/rationale.html says "After developing your application for a while, check in the application together with the Gemfile and Gemfile.lock snapshot. Now, your repository has a record of the exact versions of all of the gems that you used the last time you know for sure that the application worked."  My .lock file may have different versions, so it's probably better for one of the core developers to commit their Gemfile.lock.