Run the qunit tests from command line

This isn't quite done yet, but it's getting there. I know we still need to:

- [ ] Fix the tests that were broken by upgrading qunit (empty test blocks are no longer allowed)
- [ ] Document how to install and set up phantomjs on Windows, Mac and Linux
- [ ] Install phantomjs on the jenkins server
- [ ] Include `rake test:qunit` in the jenkins run
- [ ] Make the result of `rake test:qunit` fail the build on jenkins