Configure Travis CI to pass build

[compostbrain]

Currently build is failing. My sense is that this is a config issue.

[crawfoal]

I'm pretty sure that this is because environment variables set up in the repo settings aren't available to forks and the Postgres user and password environment variables need to be accessible to PRs from forks. I don't have access to the repo settings, so I can't see what they are set to, but here is how you can do it: https://docs.travis-ci.com/user/environment-variables#Defining-public-variables-in-.travis.yml