def plural(rule, replacement)
      @uncountables.delete(rule) if rule.is_a?(String)
      @uncountables.delete(replacement)
      @plurals.insert(0, [rule, replacement])
    end
def plural(rule, replacement)
      @uncountables.delete(rule) if rule.is_a?(String)
      @uncountables.delete(replacement)
      @plurals.insert(0, [rule, replacement])
    end
Specifies a new pluralization rule and its replacement. The rule can either be a string or a regular expression.
 The replacement should always be a string that may include references to the matched data from the rule.