Use hypothesis in the tests

[asmeurer]

Right now the tests in the test suite all use hard coded examples to try to hit different code paths. But the tests could be a lot more robust if they made use of hypothesis.

An easy place to start here would be the (currently very slow) reshape tests, which use a hard coded parameterization of different values, but could easily just use hypothesis strategies.

More generally, we would need to create some hypothesis strategies to represent the process of creating versions/datasets, perhaps by making use of state machine strategies.