Format pvalue as a string with the correct number of decimals.
Note
Deprecated in scikitbio 0.2.1dev p_value_to_str will be removed in scikitbio 0.3.0. Permutationbased pvalues in scikitbio are calculated as (num_extreme + 1) / (num_permutations + 1), so it is impossible to obtain a pvalue of zero. This function historically existed for correcting the number of digits displayed when obtaining a pvalue of zero. Since this is no longer possible, this functionality will be removed.
Number of decimals is determined by the number of permutations.
Parameters:  p_value : float or None
permutations : int


Returns:  str
