Fix tests on Ubuntu 12.04 LTS

Finally get Travis builds to work correctly. The problem was Mercurial 2.0.2 on Ubuntu 12.04 LTS not working as Mercurial 2.8.2 on Ubuntu 14.04 and Mercurial 3.0.2 on OSX does. For example, 2.0.2 doesn't give parents in our `hg log` template.