Add continuous integration

[ArthurSmid]

Integrate Travis CI (Continuous Integration) on portlandconsul for our automated tests. We want to make sure that whatever changes we make pass the tests so our changes don't cause problems, they only improve the codebase. Travis CI is already configured to run the tests, we just need to enable it on CodeForPortland.

"Continuous Integration is the practice of merging in small code changes frequently - rather than merging in a large change at the end of a development cycle. The goal is to build healthier software by developing and testing in smaller increments. This is where Travis CI comes in."
https://docs.travis-ci.com/user/for-beginners