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Another small bug fix release.
* lists(elements, unique_by=some_function, min_size=n) would have raised a
ValidationError if n > Settings.default.average_list_length because it would
have wanted to use an average list length shorter than the minimum size of
the list, which is impossible. Now it instead defaults to twice the minimum
size in these circumstances.
* basic() strategy would have only ever produced at most ten distinct values
per run of the test (which is bad if you e.g. have it inside a list). This
was obviously silly. It will now produce a much better distribution of data,
both duplicated and non duplicated.