Fixed some issues related to threading in game clock by using a queue

lib/game_clock/clock_proxy.rb

@@ -1,13 +1,20 @@
 module TAC
   class PracticeGameClock
     class ClockProxy
+      attr_reader :queue, :clock
+
       def initialize(clock, jukebox)
         @clock = clock
         @jukebox = jukebox
 
+        @queue = []
         @callbacks = {}
       end
 
+      def enqueue(&block)
+        @queue << block
+      end
+
       def register(callback, method)
         @callbacks[callback] = method
       end