text: Title: `create_result` returns x with lowest observed f(x), not lowest predicted f(x)
  Body: This seems wrong to me. The optimizer seems to be aware of its uncertainty, re-evaluating the "fluke point" and discovering that it's actually not usually that great. But then it gives me the fluke point at the end! This is especially problematic when variance is non-uniform and lower near the true minimum.
  
  Ideally, the convergence plot would be updated as well, showing the expected minimum as well as the variance around that estimate. This would lead to the convergence plot being non-monotonic, but it would converge on the true minimum rather than some other point.