[FLOC-1070] Acceptance test runner.

The tutorial Vagrantfile hard-codes the version of the tutorial base box, which means that it needs to be edited to run tests against other versions.

This provides a new Vagrantfile, and a test runner that invokes it. Hopefully, the new runner should also be able to deal with cloud VMs eventually too.
Is this going to work if the command is launched via `sudo` from a virtualenv environment? Do we need to ensure that trial is run using the same python interpreter that's running `run-acceptance-tests`?