Add before_reload, after_reload, and around_reload callbacks

[seanpdoyle]

This commit introduces three additional callbacks for the sake of parity
with other lifecycle methods:

• before_reload - evaluated before re-fetching the resource's data
  with a GET request

  class User < ActiveResource::Base
    before_reload -> { throw :abort }, unless: :id?
  end

• after_reload - evaluated after re-fetching the resource's data with
  a GET request

  class User < ActiveResource::Base
    after_reload -> { Rails.logger.info("Congratulations, the callback has run!") }
  end

• around_reload - evaluated around re-fetching the resource's data
  with a GET request

  class User < ActiveResource::Base
    around_reload :log_reloading
  
    schema do
      attribute :email, :string
    end
  
    def log_reloading
      Rails.logger.info("Reloading user with email: #{email}")
      yield
      Rails.logger.info("User reloaded with email: #{email}")
    end
  end

[rafaelfranca]

You forgot to explain why those callbacks are useful. Can you please provide a use case?