Refactor and write tests

[serin-delaunay]

At the moment everything is done by two classes, and neither one is tested. The Wangview class should be split up, each class should have its own notebook/module, and they should all be tested.

[serin-delaunay]

After #11 this issue can probably be fixed just be adding tests. However, making the terrain container a more encapsulated class would help to make #1, #3, and perhaps #5 easier to implement.