Extend serializable_hash methods in order to pass parameters to methods

Hi,

Many times I need to call methods with parameters using `as_json` but cannot because the API is not expecting this behavior.

Here is the API I am suggesting:
````Ruby
class User
   attr_accessor :name

  def initialize(age)
      @age = age
  end
  
  def make_me_older(years)
    @age + years  
  end
end

User.new(10).serializable_hash(methods: [:age, [:make_me_older, 10]]
=> {"make_me_older"=> 18}
````

This idea is to pass an array where the first element is the method name and all the other elements are parameters to the method.

Greg