More high-dimensionality tests

[kbarbary]

The test suite currently includes a few "integration tests" - full problems with known analytic evidence as a benchmark - but only in low dimensions. (Though a moderately high dimensional case is included in the examples section of the docs.)

Should add some high-dimensional problems to the tests, ideally ones that exercise the multi-ellipsoidal method. The likelihood function could be overlapping gaussians to create a curving degeneracy, which should result in multiple ellipsoids.