Remove Player.all and Game.all

Though these may have been convenient in simple examples, they stored
all Objects initialized permanently, so was unfit for real applications.

lib/elo/helper.rb

@@ -1,23 +1,11 @@
 module Elo
   module Helper
-    def self.included(base)
-      base.extend ClassMethods
-    end
-
     # Every object can be initialized with a hash,
     # almost, but not quite, entirely unlike ActiveRecord.
     def initialize(attributes = {})
       attributes.each do |key, value|
         instance_variable_set("@#{key}", value)
       end
-      self.class.all << self
-    end
-
-    module ClassMethods
-      # Provides a list of all instantiated objects of the class.
-      def all
-        @all ||= []
-      end
     end
   end
 end

spec/elo_spec.rb

@@ -34,9 +34,6 @@
     expect(bob).to be_starter
     expect(bob.games_played).to eq(8)
     expect(bob.games).to eq([game1, game2, game3, game4, game5, game6, game7, game8])
-
-    expect(Elo::Player.all).to eq([bob, jane])
-    expect(Elo::Game.all).to eq([game1, game2, game3, game4, game5, game6, game7, game8])
   end
 
   describe 'Configuration' do