Fixes https://github.com/pyugrid/pyugrid/issues/21

Travis uses Ubuntu 12.04 LTS. So I tested on such an instance using a Vagrant box and found the dependencies for a Travis build. I then constructed the .travis.yml in a branch and ran the validator at http://lint.travis-ci.org/ and passed. When I pushed the commit in this PR to the branch, the addition of the .travis.yml file triggered a Travis build which passed in 4 min 46 secs on an apparently slow guest box. You can see the results at: https://travis-ci.org/pyugrid/pyugrid . I did get a default automated email notification, but did not see a notification on IRC.