Changed

• Balanced orderings by default. n_permutations now defaults to "auto",
  which evaluates a balanced set of orderings (a Williams design): every option
  takes every position, and follows every other option, equally often. That is K
  orderings for K options, or 2K when K is odd, independent of how the criteria
  are written. Pass an integer, such as n_permutations=8, to sample permutations
  as before; "all" still enumerates every one.

Fixed

• Choices with many options no longer fail with "Backend probabilities must sum
  to approximately 1" when the API's two-decimal rounding leaves the sum at 0.99 (#1).