Check invariants for simple synthetic datasets

[emilyfertig]

For each of the simple datasets from #159 (not the final CrossCat one), write a test that runs HIRM inference and checks the following invariants:

• Has 3 unique cluster IDs
• 99% correct assignments of rows to clusters

For the multi-column case, note that this test should not infer views -- all columns are in the same view (so this tests the IRM special case of HIRM).