SlotLanguage reborn in the Machine

Just added the compiler, that can parse Slot directly into SlotMachine code (no language layer in between)
Still unclear wheather the Maker is a thing, but since it was in the Language layer i did not remove it (yet)
Otherwise just the compiler and all the tests, moved from the slot_language.

lib/slot_machine/slotted.rb

@@ -21,7 +21,7 @@ module SlotMachine
 
     def initialize( slots = nil )
       return unless slots
-      raise "stopped" unless slots.is_a?(Array)
+      raise "stopped #{slots.class}" unless slots.is_a?(Array)
       first = slots.shift
       raise "ended" unless first
       @slots = Slot.new(first)