Set up Travis to run tests written in googletest

[alexlenail]

Here's an example of how to set this up:
https://github.com/muflihun/easyloggingpp/blob/master/.travis.yml

[alexlenail]

@ludwigschmidt are you interested in learning travis or should I handle this?

[alexlenail]

I basically copy pasted that demo into a draft version and set it up with travis:

https://github.com/fraenkel-lab/pcst_fast/blob/master/.travis.yml

I'd love if you took a look -- I feel like you might be able to find the mistakes in the dummy version faster than I, but if you'd prefer me to let me know.

[ludwigschmidt]

I took care of the C++ tests, travis reports them to be passing now. Can you take care of the Python tests since you also did the pypi setup? Thanks!