Upgrade build system from qmake to cmake

CMake allows for a little more flexibility as opposed to qmake. For example, you can bundle specific versions of the dependencies at compile-time, which makes the builds both a little easier (you no longer have to manually install deps) and more reproducible. :)

I see you have "set up CI builds" in your backlog. I think this will also get rid of a lot of headaches if you choose to implement CI.