Turn on Travis CI

[ErikBoesen]

We use a helpful web application called Travis CI (Continuous Integration) to automatically test changes to our code. This is very helpful during competition season: if someone makes a pull request (request to change the code) that would cause the robot to crash, there will be a helpful red X next to the PR and the offending commit (code update) to warn us that maybe it shouldn't be applied yet and further changes are necessary before we can merge (approve) the PR.

You can look at the way we do this in 2018-robot for an example; it should work pretty similarly here. You will need to turn on Travis for this repository; Google how to set up Travis CI for instructions on this.