Automate unit tests

[Jebbs]

Currently Travis CI/Appveyor will build the unit tests, but it can't run them as it needs user input for some tests.

There are two ways I can think of to handle this:

• Remove interactive tests and just assume they work (they work for SFML)
• Mimic user input during the tests

The first is easier, the second sounds more reliable for catching things. I'm actually considering working on a separate project for simulating user input (mouse and keyboard), one that would be cross platform.

We could also do them in succession. Remove interactive tests now, find/create a way to perform interactive tests on all systems, and then add interactive tests back in.

[Jebbs]

I'm not sure how viable this is through Travis CI and Appveyer.

Tests are able to run, but most of them fail miserably due to a lack of a real audio device, some look like they're failing due to a lack of a graphics device (even with xvfb).

I'm going to put this on the back burner for now, and look into something before the release after next.