Integrate with Travis and AppVeyor

Let's integrate with Travis and AppVeyor for automated testing and release building. Relevant [blog post](https://cylonjs.com/blog/2014/11/19/creating-multiplatform-precompiled-binaries-for-node-modules/) explaining how to set something like this up. The main inspiration is from node-sass and the [p120ph37/robot-js/prebuilt](https://github.com/p120ph37/robot-js/tree/prebuilt) branch.