Better lint

[bf4]

Extracted from
https://github.com/rails-api/active_model_serializers/pull/1004/files#diff-56455571c4ba7a2b4c640b9e8168f522R40

      actual_arity = resource.method(:read_attribute_for_serialization).arity
      if defined?(::Rubinius)
        #  1 for def read_attribute_for_serialization(name); end
        # -2 for alias :read_attribute_for_serialization :send for rbx because :shrug:
        assert_includes [1, -2], actual_arity, "expected #{actual_arity.inspect} to be 1 or -2"
      else
        # using absolute value since arity is:
        #  1 for def read_attribute_for_serialization(name); end
        # -1 for alias :read_attribute_for_serialization :send
        assert_includes [1, -1], actual_arity, "expected #{actual_arity.inspect} to be 1 or -1"
      end

Correct cache_key lint for ActiveRecord 4.1+

https://github.com/rails/rails/blob/4-0-stable/activerecord/lib/active_record/integration.rb
def cache_key

https://github.com/rails/rails/blob/4-1-stable/activerecord/lib/active_record/integration.rb
def cache_key(*timestamp_names)

[joaomdmoura]

Nice, thank you @bf4, merging it

[bf4]

wee!