Add Travis Beaker tests back

[petems]

From reading the modulesync docs, it should be a matter of adding this a .sync.yml:

---
.travis.yml:
  includes:
  - rvm: '2.1.6'
    sudo: required
    services: docker
    env: PUPPET_VERSION="3.8.4" BEAKER_set="centos-6-docker-x64"
    script: bundle exec rake acceptance
    bundler_args: --without development
  - rvm: '2.1.6'
    sudo: required
    services: docker
    env: PUPPET_VERSION="3.8.4" BEAKER_set="ubuntu-server-1204-docker-x64"
    script: bundle exec rake acceptance
    bundler_args: --without development

Then running modulesync again...

[wyardley]

I redid the spec_helper_acceptance, but there are some tests that fail, so this should be looked into. We should update OS versions too, if this is something that's still in use.